I think there's no need to stress test before OC unless you want to check temperatures or whatever for comparison.
Those 2 programs serve a different purpose. Prime95 causes stress so it is used to test stability while CPU-Z just provides useful information about your components. You will also need a temperature reading program like Core Temp or Real Temp.
The do's and donts are very simple: read everything you can before OC,watch out for temperatures and be very careful with voltages.You can also search online for what other people have managed to do with your setup so you know what you can/can't do