try the book "healthy sleep habits, happy child" by dr weissbluth.
many kids are "done" with naps by the time they are 3, but i know plenty of kids who nap (or could really use a nap) who are older. My sister has 9yr old twins, plus a 2 yr old and a 6mo old. the 9s don't nap, but there is "quiet time" in the house. you don't have to sleep, but no TV, quiet reading/lying down in your room. when my son was transitioning, around age 3, it was a nightmare! he was cranky, so i was reluctant to take him anywhere, but he wasn't asleep either, so i couldn't get anything done. arg! my dtr is 3+ and still naps, with a skip now and then. i found that on days she does nap, it's a good nap, 2.5 hrs. when she does not get a nap, i put her to bed 30 mins earlier. it makes a huge difference.