OK, so RV Toilets isn't a very polite or palatable subject. You might even ask, quite appropriately, who gives a crap? However, there are several things newbies should know that will make life on the road -- and in camp -- more pleasant.
First of all, most RV toilets are not made of porcelain like home toilets. They are made of plastic. One reason for that is it makes them a lot lighter and saving weight in an RV is important. However, that means they have special cleaning requirements. You can usually use most liquid toilet cleaners safely (although some may not be compatible with holding tank chemicals), but never use harsh cleansers which will mar the finish. Once scratched it is almost impossible to restore and will collect unpleasant deposits. Use something liked a "Softscrub" cleanser, Bon Ami ("Hasn't scratched yet"), Bar Keepers Friend, or a Mr Clean Magic Eraser for stubborn stains. That said, there is an increasing tendency toward the use of porcelain toilets in RVs so you might come across one. If you do, clean it was you would the one at home.
Although RV toilets look a lot like your toilet at home, there is one very major difference: residential toilets use a lot of water for flushing (about 3 gallons in current models, up to 5 in some older ones). RV toilets use very little. Conserving water is, of course, a good thing, but it does mean solid wastes sometimes pile up in the holding tank below the toilet if you don't use enough water when flushing. If you notice this happening, you might want to draw a bucket of water off your gray water tank and dump it down the toilet. It will help to break down the accumulation and provide sufficient liquid for the holding tank chemicals to do their job breaking down waste. Since the bowl doesn't automatically fill like a residential toilet, you may want to add more before using the toilet so there is enough water to capture solids and reduce odors before the toilet is flushed. That also helps make sure there is enough water being put into the black water holding tank.
One other major difference: your residential toilet flushes into an essentially endless sewer system; your RV toilet flushes into a limited holding tank. Unless there is a stoppage in your sewer at home you usually don't have to worry about things backing up. Even septic tanks are usually large enough that you flushing a toilet won't cause a backup. The limited holding tanks on RVs means you need to always be aware of the possibility of a back up in the holding tank. With that in mind, it is prudent to make use of campground facilities whenever possible to reduce filling your holding tank,
When you flush an RV toilet, the water will keep running a little after you release the foot pedal and the valve closes. This is not a malfunction. It is designed to do that to leave about a half inch of water in the well in the bottom of the bowl to provide an air tight seal to prevent odors from the holding tank from escaping into the toilet -- and from there into the interior or the RV! You can press the pedal down part way to add more water too. You really only need about an inch on top of the valve to provide an odor seal even when the vehicle is moving. Adding more at this time is usually just a waste.
The plastic lid and seat often becomes discolored over time. Sometimes you can safely restore the appearance by cleaning plastic parts with vinegar or lemon juice. Lemon juice has the advantage of leaving a more pleasant citrus fragrance. It is unlikely a standard toilet set will fit an RV toilet. If yours is damaged, seek a matching replacement from your RV store or track one down in a junk yard. There is really no reason you couldn't use a residential toilet seat if you can find one that fits.
To avoid stains sticking to the toilet bowl in the first place, always press down the flush pedal part way to run a little extra water in the bowl before using the toilet for solid waste. That will coat the walls of the bowl with water to minimize stuff sticking to the bowl. Don't push the pedal down too far or you will open the valve and all the water will escape. Then keep a toilet brush or a dowel handy to clean stains after use. Use the dowel to swab the bowl with a little toilet paper. That way you don't put smelly deposits on a brush that will be left sitting in a container behind the toilet. You can simply flush the toilet paper. I installed an old dirt bike hand grip for extra comfort on the 3/4' quarter round dowel we use in our RV. The two square edges of the quarter round dowel grip the tissue and give a precision cleaning. The grip gives you something to hold on to and prevents you from grabbing the dirty end!
Some RV toilets have a sprayer like the one on your kitchen sink that you can use to aid in cleaning the bowl. These get mixed reviews. While the sprayer may add convenience to cleaning it sometimes encourages excessive water use and you have a couple more plumbing connections that might be prone to leak. If your RV toilet doesn't have one and you REALLY want one, it can probably be added. I decided it wouldn't be worth the cost. Even now that I have an RV that came with one I still feel the same way. I find it adds some convenience but it is too easy to waste water. I use it occasionally but if my next RV doesn't have one I probably wouldn't miss it. Even with the sprayer, it is usually faster and more effective to clean the bowl with a bit of toilet paper on a dowel as described above.
Don't put facial tissue in your RV toilet. It will not break down as easily as toilet paper and can cause buildups and clogs that are difficult to remove when you dump the tanks and can block sensors so you don't get an accurate reading on your gauges.
Speaking of toilet paper, it is best to use the toilet paper designed for RV toilets. If you run out, use the cheapest and lightest weight paper you can find. The fancier, multi-layer brands won't break down well and may contribute to clogs and difficulty dumping the black water tank. Plain single ply is best. If you have any question about whether a particular toilet paper is safe to use in your RV or what it will do, you can test it easily yourself. Just put a couple of squares of toilet paper in a glass jar about half filled with water. Shake it for a half minute or so. It the paper breaks down, it will be OK. To see what unacceptable paper will do, try the same test with an ordinary facial tissue like Kleenex. It won't break down no matter how much you shake it. Stuff like that will clog your black water system or porta-potti.
NEVER put disposable diapers or feminine hygiene products down an RV toilet. Or not even "flushable" baby wipes. Once again, these products won't break down in the holding tank and will cause clogs and bad odors.
Even so-called "flushable" wipes should NOT be flushed down an RV toilet. They might be OK in residential sewer systems but are likely to clog RV holding tanks. Standard sewer systems use significant amounts of water that are capable of moving things that would clog an RV holding tank.
Here's a tip for guys: to avoid urine smell buildup around your RV toilet, sit down to urinate. OK, so it may not be the most macho thing to do, so what? Its private. And it can keep things a lot nicer. No matter how good your aim is, it still splatters and over time the residue from the mist builds up on cabinets, walls, and floors. You will also find it especially convenient for nocturnal trips when you don't want to turn on any lights. Your female companions will definitely appreciate having a clean smelling bathroom.
You may have a tendency to limit water usage when flushing to conserve your fresh water. While conserving fresh water is almost always a priority when boondocking, using too little water will create problems in the black water tank, ranging from th buildup of a pyramid of waste right below the toilet to not having enough liquid for the chemicals to their job or to flush the tank when the time comes. You don't need extra water for liquids only, but it is essential when there are solids in the toilet, It may take a little experimentation to determine the right balance between conservation and adequate flushing. It is usually a lot easier to err on the side of using too much water and slowly backing down than having to deal with too much solids building up in the tank. Too much water in the holding tank will not cause any problems with dumping, but too little definitely will. The only problem with using too much water is using up your fresh water and filling your holding tank when boondocking or when on the road. Too little water also impedes the function of holding tank chemicals, which break down solid waste and control odor. If you think you are short of water in the black water tank (as evidenced by piles of solids seen beneath the toilet when you flush it), try adding some extra water collected while warming up your shower or even draw a bucket off your gray water tank and dump it down the toilet. I have found that, in general, filling the bowl about half full before using the toilet provides enough liquids for proper operation but your experience may vary.
Odor control for an RV toilet is definitely a consideration. Not only do you have the natural odors associated with its normal use, it can be a source of foul odors from the holding tank if not used properly. To reduce odors from normal use, run a little extra water in the bowl by partially depressing the foot pedal before using. Then make sure there is a little water left in the bottom of the bowl after you flush it. The water acts as an air-tight seal to prevent odors from sneaking past the closed flush valve. You can also shoot a light spray of air freshener into the bowl and holding tank when you flush it. But don't over do it. There is no telling what effect the chemicals in the air freshener might have on the holding tank chemicals. Speaking of holding tank chemicals, make sure you are always using sufficient holding tank chemicals for the condition of your tanks. Read the label on your chemicals to find out how many gallons each treatment can handle and add more chemicals proportionately if your holding tanks are larger. You may also need to add extra chemicals in hot weather as the heat tends to promote rapid and powerful odor build up. Most RV bathrooms have a roof vent to allow odors to escape. Many are equipped with a 12-volt fan to aid in evacuating toilet odors and shower humidity. If your RV doesn't have a vent one can usually be added. If you have a vent but no fan, a fan can be added to an existing vent. That is the simplest and most economical solution but for better air flow and quieter operation choose a Fantastic brand (or similar) power roof vent. They have large (10") multi-blade fans that move a lot more air than the little 4", 4-blade standard add-on fans. However, even the little add-on fans will help to some degree. You will not want to leave the roof vent wide open when you are trying to either heat or cool your RV or when it is raining. It is especially bad when heating because heat rises and the forced air furnace will push the hottest air in your RV out the vent, causing the furnace to have to work harder. DO open the vent as needed for toilet use, but don't routinely leave it open.
You will sometimes get holding tank odors in your RV while driving. The most common cause of this is driving with one or more windows open. It creates a partial vacuum which literally sucks odors out or your holding tank. Sometimes odors are drawn back in from the standard roof vent. There are some after-market holding tank vent "caps" that help dispel odors and prevent them from being drawn back into your RV. The standard vent cap is just a plastic cap that is a bit larger than the pipe so air can escape. One of the upgraded caps is designed aerodynamically so it swings into the wind (natural or from driving) to ensure the odors are pulled up and out and directed safely away. These upgraded caps usually cost around $25 and an be generally be installed by a competent do-it-yourselfer and are well worth the investment!
Air fresheners are a common remedy for bathroom odors. You can usually find a variety of scents at your local Dollar Tree so they don't have to be expensive and you can experiment to see what scent you like best. When ever using an air freshener, use it sparingly. You don't want the mist to settle on everything. Over-use of air fresheners often creates an odor combination that is more offensive than the original holding tank odor. Think of a strong floral scent blended with sewer smell! Yuck!
Some smaller RVs, like tent trailers, may have a portable toilet. Most of what has been said about RV toilets applies to porta-pottis as well. So, if keep that in mind if you are using a porta-potti in your small RV, tent, or boat.
Enjoy your RV "throne".