Searching for information is often nonlinear and iterative, requiring the evaluation of a range of information sources and the mental flexibility to pursue alternate avenues as new understanding develops.
--- ACRL Framework for Information Literacy for Higher Education
Remember to always evaluate what you find on the Surface Web when you are using search engines for research purposes.
Limit your search results to organizational or educational websites.
Add "site:.org" or "site:.edu" behind your search term
example: bird flu site:.org
1. Use "refine tools" and "search options"
2. follow the specific language (subject terms) used by different databases
3. Click "360 links" for checking the full-text
4. check reference list of articles