It's possible to find a large amount of information, but seldom "everything". To cover your subject of interest best, it is therefore important that you reflect and plan your information searching to gain as much relevant information as possible.
The information search process
Before you start searching, take the time to reflect about the following:
The first step in the information search process is always the question or issue you want to address: What makes a research question good? Which criteria are applicable? Is it possible to answer?
Encyclopaedias and subject thesauri can be a good start to get suggestions for keywords and main concepts. Some databases has indexes or so called thesauri to help you find subject terms suitable for that database. Also remember to figure out synonyms and variations for the search words.
Before you start searching, think through what kind of information you are looking for. Which sources and literature may be useful? At the starting point of the material gathering process, dissertations, academic papers/essays and reference works are good staring points to learn about and get familiar with a new subject area. Reference works, that is subject specific encyclopaedias and handbooks, are very useful to get an overview of a research field. You will find comprehensive articles about the research within an issue and provide references for further reading.
To optimize your searches it is appropriate to get familiar with the most common search techniques. Most search services have a "help session" or an on-line tutorial where it is explained how to which search techniques should be used and how to use them. Common search techniques are boolean search, phrase search and usage of truncation and wild cards.
The search process is seldom straight or simple, you might have to redefine your search terms as you go. Remember to save your searches, search words and results.
Truncation means that you replace the end of a word with a sign, usually the * sign, alllowing you to search everything starting with a certain stemming.
If you write socio* you get sociology, sociological, sociopath etc.
You use phrase search when you want specific words to appear in a specific order. Most databases mark phrases with quotation marks "" before and after the phrase.
"climate change" gives hits for this phrase, but not for the words in other contexts like changes in the climate generally.
"Karl Marx" gives hits for this specific name in this specific order, but not for the Marx brothers or other persons named Karl.
Databases are constructed by entering data in different fields. There are author, title, year and abstract fields (and many more). You can use these fields for limiting your search.
When searching for Michel Foucault you can choose the author field for finding articles by Foucault himself, the abstract field for finding articles mentioning him or the title field for finding articles where he is a prominent figure.