Learning to do derivations is seldom easy for students. The best way to learn is by doing. Dig into the exercises! But you may find that there are times when even the many hints available for the canned problems are insufficient.
When that happens, it's best to watch someone else do a problem, then try to reproduce the results on your own (without looking!). Here are some derivations which are done for you and explained. Try to understand what went on in the demonstration, then reproduce them on your own.
PD Derivation Demos: