Wi-Fi on the blink!

Wi-Fi connection is very inconsistent, but mostly not connected even when right beside the access point. But it does connect at times, as if nothing was wrong. Then most times it can't find any wireless sources at all. How should I go about evaluating this problem? I am guessing maybe a loose antenna connection? Or is it the communications board? Or the logic board itself? I hope not! Any tips, anyone? Thanks!