To gain an overview of content and vocabulary, especially when searching a new topic, consider searching...
Subject encyclopedias or other reference works (handbooks, dictionaries, etc.)
Consult with scholars in the field (e.g. your advisor).
When consulting the literature, you will also get foundational knowledge of the seminal theories, authors, works and themes on that topic.
Brainstorm search terms
It's a good idea to keep track of the search terms you use when looking for information because it will increase the relevance of your results and save you time overall. You can do this by noting the database(s) you used and the successful terms in a search log.
When you find an article or resource that is relevant or close to what you're looking for, note the subject terms, or author-supplied keywords associated with it. You may have to search for awhile before hitting upon the best search terms for your topic. Be sure to try that term in databases you've already searched!
How do you keep track of search terms? You could save them in a Google Document or you could save your searches in the database in which you're searching. To save searches in a database, you will have to create a free account in the database.
Sometimes in research one can have a very specific topic such as Food Banks in Nampa, Idaho. Being so specific may provide practical relevance but you might not encounter research articles specific to Nampa, Idaho. The idea is to take the central topic and apply it to the area of interest. Broadening your search strategy to such things as: Food Programs, Hunger, or Nutrition can often lead to relevant results. If you are interested in a specific geographic location expand your search to include: Idaho, Northwest, West, or United States. As a researcher you will need to compare and contrast the similarities and differences you in relation to your specific area of interest. Follow this link to a website which talks about broadening a topic in a bit more detail.
Remember, refining your research topic or question is an ongoing process. As you conduct your literature review, you may find that you need to narrow or broaden your topic. Don't be afraid to ask for help!
Reference Ebooks: dictionaries, encyclopedias, and more!
A collection of encyclopedias classified by Business, Education, Environment, History, Literature, Medicine, Multicultural Studies, Nation and World, Religion, Science, and Social Science. Full-text searchable and browsable.
Contains digital facsimile page images of virtually every work printed in England, Ireland, Scotland, Wales and British North America and works in English printed elsewhere from 1473-1700. (Description from their website)