This is tough. I have two - almost 3 and 1 and 1/2. So I have just a little experience.
I should first say that I am not a fan of the cry it out method, and feel if our children are crying we need to first understand why. Having said that, if you know he's not sick, wet, dirty, hungry etc. he is likely wanting more attention. With my first I picked her up every time. With my son, we did give him some time to put himself down again - and he eventually did. Once we knew he was safe and healthy, we would leave him for a time. I struggled with this, but it helped to look at the clock and pick a time 2, 5 10 minutes and make myself wait to go get him. Eventually, he would learn to put himself back down. He now sleeps through the night 7:30 - 5:30 (early, but solid sleep).
Just be sure the crib mattress is low enough he can't climb/fall out!
Good luck, and follow your instincts about why he is crying. No right answer, just what works for you guys.