The University at Albany has a guide:
SEARCH ENGINES, SUBJECT DIRECTORIES & THE DEEP WEB
Getting Started: Selecting a Tool for Your Search
A chart listing general query types and the kinds of search tools that support them
http://library.albany.edu/internet/start... Boolean Searching on the Internet
The principles of search logic and the different manifestations of this logic on Web search engines
http://library.albany.edu/internet/boole... The Deep Web
A tutorial describing this newsworthy phenomenon: what it is, what to call it, tips for dealing with it, and how to locate its content
http://library.albany.edu/internet/deepw... How to Choose a Search Engine or Directory
A chart listing numerous features and the search engines & directories that support them
http://library.albany.edu/internet/choos... Searching the Internet: Recommended Sites and Search Techniques
An extensive tutorial on the use of subject directories, search engine services, and the "deep" Web. This tutorial covers Google, Ask Jeeves, BUBL LINK, Ixquick and Yahoo
http://library.albany.edu/internet/searc... Second Generation Searching on the Web
Tips on precision searching using features available on second generation search services. This tutorial covers Teoma, Ixquick, SurfWax and TracerLock
http://library.albany.edu/internet/secon... Hope that helps.