I don't understand why inheritance is always taught before composition. I almost never reach for inheritance these days, composition winds up more accurately modeling the domain. I'll define a bunch of classes modeling the actual behavior of domain objects, then get some code working using those classes. Then I'll start cleaning up, figuring out what goes together and creating composed classes out of the individual pieces of behavior. As I'm doing this, a lot of times I'll pull out functionality in one class and put it where it seems to belong.