Learn 2 engines well. Bookmark your favorites. Resist the urge to use one engine exclusively.
For comprehensive or obscure searches, use them all - and consider the Meta-Search engines that simultaneously search multiple search engine databases.
Read (and print out) help screens and FAQs.
Use the most specific terms possible - and combine them with and (+),or,not (-). Put quotation marks (" ") around words you wish to search as a phrase.