K.P.
I hate hearing my little guy cry but I know in the end it is a good thing. When I lay him down I say it is nap time and will check on you after x amount of time. I then lay him down and leave. I do watch the clock and after the x time if he is still crying I go in and pick him up and hold him and rock him for a minute and then do it all again. My little guy only needed me a few times.
Hope this helps. I did 5 minute at a time. If I wanted to try longer I would have to stand in the shower so I couldn't hear him cry.