Bryan Garner has a post up at the ABA Journal on legal writing. We especially like tip number 2:
2) Don't rely exclusively on computer research. Combine book research with computer research. Don't overlook such obvious resources as Corpus Juris Secundum and American Jurisprudence. Look at indexes, digests and treatises to round out your understanding of the subject matter. And when it comes to computer research, don't forget Google Books (especially the advanced-search function): It can open up a great variety of fresh resources in addition to what you find with Westlaw or Lexis.
The Law Library has several books by Garner and on legal writing in its collection.