I think Fred Sanders' advice is very good:
1. Pick a major doctrine to focus upon.
2. Read classic texts and things that you will perennially return to while trying to stay current wight he recent literature on the doctrine. Realize that mastery might be impossible, but keeping within the main current is not.
Sanders uses the example of his own discipline, which happens to be my doctrinal interest, the Trinity.
Also, don't miss his comments about the importance of studying the biblical languages.
