Wikipedia is a great site for getting basic information about your topic, especially if your topic is one that is new to you.
Use Wikipedia entries to find keywords, alternate spellings, and important people or places that are related to your topic. These keywords are what you will use when you start searching for books and articles.
Another rich source of information in Wikipedia is the sources listed at the end of the article in the Bibliography and/or the References section.
Join keywords with AND, OR, or NOT:
legalization AND marijuana
marijuana OR cannabis
marijuana NOT recreational
Put quotation marks around phrases to search for the words side-by-side:
"capital punishment"
"death penalty"
Try different words or phrases:
capital punishment, death penalty, execution
Use an asterisk:
teen* will find teen, teens, teenagers
Check your spelling!
Try more than one database.