Before you touch anything to do with clocking make sure you have adequate cooling. A non standard CPU Cooler, case with *lots* of airflow... Failure to keep your equipment properly cooled will result in crashes, hangs, poor performance and possibly ruined equipment. And since warranty's are voided by OCing it can be risky.
the RAM will run stable at either 1600MHz or 2000MHz. What I do when clocking is increase it by small amounts, and let it run for an hour or so and check to see how my temps are doing. Then stress test it (usually playing a game) while monitoring temps.
If you have specific questions about clocking, I would suggest the OverClocking thread, as there are guys there that should be able to give you exact numbers.