One thing to start out with is to make sure you know what you are actually searching. The WSU Libraries catalog "Search It" has multiple scopes so you could be searching everything (the default) or you can limit your search using a drop-down menu to books, or stuff available at the Pullman campus only, etc. Databases and catalogs generally have facets, or limiters that if selected restrict your results - for example, to peer reviewed articles only, or things published since 2005.
Second, keep in mind your Library Database Search Toolkit:
Generate Search Terms (ongoing)
Truncation - use (usually, but not always) an asterisk to get plurals and variants: theor* will get theories, theory, theorize, etc. (Some databases may use different symbols, i.e. an exclamation mark (!). If you are unsure, look for a Help or Search Tips link within your database.
Phrase searching - enclose specific terms in quotation marks so they will be searched together so you are less likely to get irrelevant results. Don't make your phrase too specific, and make sure you don't have typos! "broken windows" theor*
Operators and Grouping: Use the AND and OR operators to get a better search. OR expands your search by letting you look for multiple terms, i.e. synonyms. AND narrows your results because you are looking for results that have both or all your terms so that your results include all concepts being searched and so are likely to be more relevant for your needs:
Simple Search (only one search box) - Use parentheses to group multiple concept terms. Note: I did spell out united states, but the text box cut it off ;-) Please note that in both examples I didn't use the asterisk (*) to search for plurals and variants, so my search could be improved.
Advanced Search Box (multiple search boxes) - Parentheses are not needed because each concept has its own search box. In this case there is a default AND between boxes, but clicking the down arrow in the box that says "contains" would let you change your operator.
Look here for a complete list of WSU Libraries Research and Resource Guides for all subjects and disciplines.
Note that think tanks and research institutes may have a (or multiple) specific policy perspective (i.e. centrist, liberal, conservative, feminist, libertarian, etc).
About think tanks - On Think Tanks