Yep, Andy has it nailed. If you suspect you are deadstick, increase throttle and pull the nose slightly up. (I mean just a little, a few degrees). It should become pretty obvious if you're engine is running or not.

When in doubt, turn immediatly towards the field. If you're in doubt, you're probibly also far from the runway, and it might be a good time to do a low- to mid-level pass down the runway. And if it turns out the engine is dead, you're at least now gliding in the correct direction.