How do you make insects come back to life?

If they're truly dead, you can't. But if they seem 'drowned' because they were held underwater until they stopped moving, you can 'resurrect' them by absorbing the water from their spiracles (breathing holes in the sides of their abdomen). I once saw a guy in Greece do this with a fly, drowning it in his drink and then taking it out and tapping the ash from his cigarette over it. After a few seconds the fly dug its way out of the ash and was on its merry way. I think this can be done with most insects as they all have spiracles and are very hardy. But there's no coming back from a slap with a flyswatter, windshield or bug zapper, or poison for that matter.

Oh, on another note, you can freeze some species for a long while and they'll still be alive when you take them out, making it seem as if they resurrect. Many species will just die in a few minutes/hours, though. Scorpions are notorious for surviving being frozen in solid ice!