You will usually get an error code. If you have speakers, the ones that attach to pins on the mobo, then put em on and boot up. Then look in the manual for the error code that you get. You can try to run with one stick at a time to see if its bad.
...And so it began, the battle for earth between two noble creatures, whos command over the internetz is known throughout the globe, but who, who will conquer the other in their quest for middle earth? Could it be edward? The mightiest of the magicians capables of creating 16 ghz super duper uber machines of pron capabilities, or shall it be videofx, master of pure action in his pants. Only fate will decide and until then the balance of power on middle earth shall be as fragile as the shell of a precious egg.