Having read through pet peeves thread, I thought I would post up what is IMO the correct way to spot. Through my time hitting the Iron I've been amazed at how many people are very shitty spotters, and this can lead to serious injury, or if nothing else a frustrated lifting partner.
Objective of the "spot": to allow another person to work to thier full potential on a given excersize safely, and with good form.
1. Get an idea of how many reps a person is shooting for, this way you are prepared.
2. As the person progresses through thier sets, take notice of thier motion, how they handle the load on thier own.
3. When fatigue sets in, and it is nessisary to assist, do so with just enough force to allow the rep to completed with correct form.
1. Do not allow the person to sacrafice form for movement. Example, if your doing skull crushers, and on the last rep you are struggling, you'd want your spot to help slightly, so you dont need to flare your elbos out inorder to complete the lift.
2. Do not "yank" the wieght away from someone. Example, On flat barbell bench, even if the bar begins to move negatively, and it is certain your partner can not lift it. simply provide enough help for them to complete thier rep. Grabbing 225 off someones chest and placing it on the rack does not help them build muscle.
3. Distract the person as little as possible. There is nothing more annoying then a spotter talking through your entire rep range. Encouragement on the last few reps may be needed, but there is no need to be a distraction, you are there to help.
4. Pay attention to what is going on. If you are asked for a spot, and are day dreaming, or shooting the shit with someone else, it can be very dangerous. (you would think this last one is a no brainer, but I see it too often to not mention it)