Peeing in stalls in a public toilet:

If you are peeing in the stall, which should almost never happen (see other post)... 

But if you happen to be peeing in a stall, be a gentleman and flip up the toilet seat. Use your shoe to gently push up the seat.

Don't be the dick who pisses on the seat. 

Some co-worker of yours may be in an Emergency Dumping Situation and need that seat in a panicked terror.