Here is my public bathroom etiquette list:
Toilets
1. Flush - As the OP has pointed out, it's disgusting. I am all about conservation and try not to take long showers, but I do splurge when it comes to toilet bowls. I flush after each trip. So please remember, the patron who comes into the stall after you has no desire to see what you ate for dinner the night before.
2. Wipe - I have come into stalls and seen your business in the bowl, unflushed. There is no toilet paper in the bowl.

We all lead busy lives. Perhaps you could wake up a few minutes earlier each day, which would give you the extra few minutes needed to wipe yourself. It would also save me from having a horrifying image burned into my brain for the rest of my life.
3. Farting - I know, sometimes a toot can just slip out when in a stall. I'm talking about the people that release their gas on an unsuspecting restroom without abandon. The bathroom is filled with a symphony of sounds that are being released, as if we are attending an extended performance of "Wishes - The Night Time Spectacular". When the farting starts, my peeing stops. I don't know why. This is really annoying because I then need to find a different restroom to complete my business.
4. Shutting and locking the stall door - I have no desire to see you conducting your business on the toilet. I have walked past open stall doors and seen grown men going about their duties (get it, duties

). Have you no shame? Nobody likes enclosed spaces, but this behavior is ridiculous. Also annoying is the surprise pooper. This is when I open a stall door and find a man on the toilet bowl. Please lock the stall door. I don't like being surprised. Also, if you are in the stall, why so silent? Why not say, "someone in here", or cough. Something. Anything. Just alert me to your presence so I don't have to see something that will scar me mentally.
Urinals
1. Proper spacing - If there is a wall with twenty urinals, and I am the only other person utilizing one, why must you pick the urinal right next to me? Again, this action will make my stream of urine stop midstream. If this is your way of trying to meet someone new, just go into any bathroom stall and jot down any of the numerous phone numbers that advertise "calling for a good time".
2. Aiming - Okay, the urinal is directly in front of you. How do you miss? Why is there a puddle of urine on the floor all around the urinal? When this occurs I am forced to take a wide stance in the restroom. We all know what happened to a certain senator that took a wide stance in a public restroom not too long ago. I do not like giving this mixed message to my fellow restroom visitors. So, if you see me in front of a urinal with a wide stance, I'm not looking for romance, I'm just trying to keep my feet out of the puddle of urine.
3. Talkers - No, I'm not interested in discussing last night's game while doing my business. I need complete concentration while performing. Talking to me just breaks my concentration, again causing a stoppage. I know that you are very excited about that last second victory, and I am truly happy for you, but leave me alone.
Sinks
1. Soap - Dipping your hands under the faucet for five seconds is not a cleaning. There is a new technological advancement that is sweeping restrooms nationwide. It's called soap. With this miraculous chemical, hands can be properly sanitized. Don't fear it. It is not the stuff of black magic or sorcery. It is perfectly safe to use and should not be feared. Soap is our friend.
2. Ignoring the sink - It is there for a reason. Your hands have been near places on your body that may not be sanitary. This is why sinks are there. Even if you are unsure whether or not you got a little too close while wiping, why chance it? Make me happy, just wash your hands to be safe.