1. Get to know the search engine you use the most. They all provide various operators that allow you to tweak the search including various ways to include or exclude certain terms or search specific sites or for specific phrases.
2. First try as specific a search as possible and broaden the search if need be.
3. Try different variations of the search terms - it helps to spend a bit of time working on your search terms.
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Relevant links:
Google Hacks - a book on getting the most from Google with sample chapters
Google Tools a collection of tools for assisting with searching Google
