Some people may find it funny, but yes, there is such a thing as bathroom etiquette. There is nothing worse in the world than having the person who used the bathroom before you is such a slob.
Flush the toilet. Nobody likes using a toilet that hasn’t been flushed. If you’re picky with what you’ll be handling, use tissue on the flush. But please, do flush after using.
For females, used feminie products should be wrapped with toilet paper before throwing them in the trash can. This will avoid toilet-clogging, and some people really don’t like seeing used feminie products.
For the males, lift the toilet lid when you are about to go, and put it down after.
Wipe faucet handles with paper towel after using. Needless to say, always wash your hands after using the toilet.
The key here is consideration. Just be considerate to other people who will be using the bathroom after you.