Search Tips and Tricks
Google's own tips page with suggestions on ways to use Google Search.
Top 26 Advanced Search Tips, Tricks, and Techniques
Explanations of many not-so-common search tools to help refine searches and make them more specific, including searching within sites, titles, text, anchors, by date, time, file type, word origin, and others.
Top 10 Clever Search Tricks
Shows how to use Google as a proxy to bypass paywalls and blocked sites, tips on using cached sites, using "vs" as a comparison, how to find free apps and files to download, and more.
Top 10 Search Modifiers: Why they matter, What they are, and How to use them
This explains many of the same concepts, but includes how to use AND, OR, and "Inpostauthor". It also has a very helpful section at the end where search tools are combined for a few different use cases.
20 Tips To Use Search Efficiently
This has a few things not covered by the others, like how to only include numbers within a certain range, using "link:" to find pages that link to a specific site, and how to increase the effectiveness of a search by keeping the terms simple.