Computerized library catalogues and internet searches have in some ways made the process of finding sources easier than it's ever been, but it's worth being aware of the limitations of computer-based methods of searching. Computers can only retrieve records which have been classified using the keyword you've typed, so your ability to use computers to find relevant material is going to depend on what you already know about the key issues in the academic field.
This aspect of computer-based searching means that if you're not very clear about exactly what you're looking for, you will need to think flexibly and try out a variety of keywords related to different areas of the topic. There may well be relevant material in books on more general topics: if you were looking for criticism on Irvine Welsh's novel Trainspotting, for example, a search on the "contemporary British novel" might well turn something relevant up. Computers can also create the opposite problem of an unmanageable mass of results, which is often found in web-based searching, so it would be worth your while to find out about the use of the Boolean search operators AND, OR and NOT.
The limitations of computer-based searching make it important that you also use the more traditional method of looking at bibliographies. Most academic books come with a bibliography at the back, which can be a quicker way of identifying material relevant to the field than relying on computer searches. There are also specially compiled academic bibliographies, such as the MLA Bibliography. Although many of these have been computerized, it can still be useful to look at the printed volumes, because this allows you to come across material that you weren't specifically looking for.
In the early stages of familiarizing yourself with an academic field it can be very helpful to read review articles, which present an extended review of the literature, or survey of work published recently in a particular area. This will give you a much better idea of what the relevant keywords are.