Wait at least 72 hours. If it doesn't start fermenting by then, THEN you can start worrying.
Also, the ONLY, (and I mean only), way to tell if it's fermenting is with a hydrometer reading. Bubbles mean nothing! Airlocks mean nothing! Check it in a few days with a hydrometer, and compare to your OG reading, (you took an OG reading, right?, if not, tell us what you put in it, and we'll tell you your likely OG).