Start off by thinking of words which describe the information you are interested in as specifically as possible. Think of as many ways of saying the same thing as possible. Use synonyms and thesauri to help you find relevant words.
Consider relevant broader terms as well. You may find information in articles or books which do not at first sight seem relevant to your research. If you are interested in information about a particular country you may want to broaden your search to include material relating to the region as a whole. If you are interested in poetry you may also find useful material under "literature".
Many databases use Boolean logic when searching for your keywords. You may not realise it, but you are already using Boolean logic. When you search the Internet or a library catalogue and you type in more than one keyword most databases assume that you want to look for material that has all of your keywords in and so when they search they add an "AND". This is one aspect of Boolean searching.
When using databases you may sometimes need to type in AND or & yourself, when looking for several keywords so please check the instructions carefully when using a new database.
By using Boolean operators (AND, OR, NOT) you can make your search very specific or much broader.
Using the operator OR between your keywords means that the database will search for material containing any of the words you have typed in. This means that you will get many more results than using AND, but they may not be as specific. E.g. film OR movies OR cinema
Using the operator NOT means that you can limit your searches to exclude words which are not relevant to your search. E.g. south asia NOT india
Truncation allows you to specify the first few letters of a term you would like to find and then the database will search for all words which start with those letters. Truncation is usually specified by an asterisk (*), but please check each database you use.
E.g. Econom* - searches for any terms starting with these letters such as Economic, Economise, Economy, Economies, Economics.
This is useful to expand a search, but be careful, you may get more results than you wanted!