When doing your research it's a good idea to have a strategy on how you want to approach it.  When planning your strategy here are some things to keep in mind.

Keyword versus Subject Searching--Do you need to do a broad keyword search where the computer searches for a string of characters with no judgment added?  Or do you need a more focused search where an indexer has read the material and indexed it under a specific subject?

Date versus Relevance--Do you want the most recent information or the most relevant? 

Scholarly versus Popular--Do you need peer reviewed articles on the results of a study, clinical trial, etc.?  Or do you need articles on the issues and controversies pertaining to your topic and/or what the lay community is thinking about it?

When doing your research, practice good record keeping.  Make it a habit to consistently capture all the citation information of all the sources that interest you.  This will help you find something quickly whenever you need to access it and will save time when you need to cite it in your work.