I have made these quite a few times and they are wonderful, but I have discovered a few useful things.
1. It works better if you can get mini-sized chocolate chips. They end up more evenly distributed than the regular sized ones.
2. If you like coconut, use it. If you don't use it, add a bit more flour. About 1/3 cup is good. The coconut makes them stickier, and if you exclude it without replacing it, they don't really stiffen in a good way.
3. This last one is only good if they are all going to be eaten in about 1-2 days. Use a high-walled (3/4" - 1") cookie sheet instead of the square pan. They come out thinner, which makes the portions more reasonable. When I tried this, everyone liked them more, but they got stale much more quickly.