You could ask yourself four questions in relation to an effective search strategy:
1. What am I searching for?
a. What is the subject of your search?
b. What types of documents contain the relevant information?
2. Where to search?
Choose the most suitable database/catalogue/website etc.: your choice is dependent on the answers to questions 1a and 1b. The library gives access to search engines for each discipline.
3. How to search?
a. Perform an efficient search: use relevant search terms and make use of the functionalities of the databases and search engines
b. There are several search methods. The bibliographic method (entering search terms in scientific search engines) and the snowball/citation search method (basing your search on something you already found) are the major ones. How to use these methods exactly depends on the options the search engines offer.
4. How do I select/assess the results?
a. Does the information you found answer (part of) your research question and
b. Is the information of good quality?
Snowball method: You search on the basis of a suitable article you have found earlier. For instance, you go looking for other articles by the same author or you search by keywords you have found in that article. Most common is searching in the reading list of the article. This way of searching for references goes back in time to older publications.
Citation searching: see if the article you found has been cited, and if so, have a look at these articles and find out again of they have been cited in their turn etc. Citation searching must be done in a citation database, like Web of Science, Scopus or in Google Scholar. This method goes forward in time to newer articles. Please take into account that a recent article may have no citations yet or just a few.
Systematic method: you search on the basis of (combined) search terms in search engines which make literature in a certain discipline (or all disciplines) searchable (regardless of availability) with the intention of finding as much literature as possible on that subject. You may expand (adding search terms you have found) or limit (cancelling search terms or filter on year of publication). You can use several search techniques in the systematic method.
When doing longer papers or a thesis it is sensible to make an explicit search profile as part of your search strategy. A search profile details:
At least once try to write all these choices down to force yourself to make them explicit. During your search you can add things or eliminate them when they do not prove fruitful.