Start with a broad search and then use facets (usually on the left-hand or right-hand side of the search results) to limit your results. It is easier to narrow down results than to start with too few results.
Take notes as you search. Searching is an iterative process and you may want to revisit and refine ideas that you come across as you search.
Try not limit your search results to just those with full text availability. Which scholarly resources are available in full text has to do with license agreements between publishers and the library, not the quality of the resource. Use Interlibrary loan (ILL) to request articles where the library does not have full text access.