1.  A urinal is a receptacle that is designed to collect and dispose of male urine.  It's not a sign that means "pee in this general direction".  You actually have to aim your appendage so your entire urine stream ends up inside the urinal. It is not acceptable to urinate under, around or on top of the urinal.
2. The appropriate urinating posture is using one hand to hang on to your pants, and using the other hand to guide your appendage, targeting the urine stream. The tip of your appendage should be above the part of the urinal that juts out.  This will prevent floor spillage due the pressure drop towards the end.  Your entire body should remain motionless during usage.
3. Urinating with your hands in your pockets and letting your appendage hang out unattended is inappropriate behavior. It increases the chance of violating rule #1, especially as the stream pressure starts to decrease towards the end.  It's also just creepy.
4. Throwing your head back, letting a big breath out and saying "aaaah, yeah" upon the commencement of urination is considered poor manners.
5. When you're done, it is acceptable to give your appendage a few shakes to get those last drops out.  However, this should be done with subdued force.  Unnecessarily vigorous shaking could result in a violation of rule #1 and might stain the shoes/glasses of others using adjacent stalls.
6. It is NEVER ok to peek over to adjacent stalls when using the urinal.  At a minimum, you must keep a steady gaze forward.  It's preferable to focus your stare on the job at hand, thereby minimizing the risk of violating rule #1. Violating this rule could get you hurt in some places.
7. It is not good etiquette to start a conversation with others using the facilities.  Anything more than a simple "hey dude" shows poor judgment.
8. Telling jokes during urination is unacceptable as it results in multiple users simultaneously, and repeatedly, violating rule #1.
9. Nasal exploratory drilling is unacceptable during urination, especially since the deposits are likely to end up in or around the urinal, or smeared at the wall/separator.
10. The name "urinal" comes from the word "urine".  It is meant to convey the fact that the receptacle is for urine only.  Therefore, any other objects thrown in the urinal will cause it to clog.  This behavior should be avoided.  (Note: This includes regurgitation, excretion and ejaculation.)
11. A urinal is a single-user apparatus. It is never acceptable to share a urinal, even if you are gay.
12. When using a urinal, it is never acceptable to stand on the sink and go for distance.
13. If the urinal is equipped with a flushing mechanism, the user is obliged to utilize it upon completion of urination.
14. Testicular exploratory scratching should be avoided. It is considered poor manners and could result in unsightly deposits of body hair and other unsanitary residue.
15. Don't drink the water. Yes, in some places this is an issue. As you can see from the photo below, one of those places is the new Olympic Oval in Vancouver, BC.

16. Don't compliment your neighbor on the size of his member: http://answers.yahoo.com/question/index?qid=20071221142315AA2yeQj

More hints, like not shitting in the urinal, can be found on somethingevil.com.