J.C.
I used 5 minutes every time, never increased to 10 or 15 because I did not want them to get too worked up and there for be hard to calm, also I wanted them to understand it was bed time while still knowing I was there for them. When I would calm them I would try to do it with out taking them out of the crib so they understood it was bed time. I would rub their tummy or back and sing or talk softly until they were calm, and than leave and if they started to fuss, I would wait another 5 minutes. When they would wake at night I would also wait 5 minutes before going in, and most of the time they self soothed and were back to sleep before the time was up. I started this almost from birth, and both of my boys were sleeping through the night by around 2 months old because they never learned bad sleep habits.
Best of luck and Blessed Be