Next to clearly stating a thesis and purpose for research, the literature review is the second most critical element to conducting successful research projects. Literature reviews demonstrate the researcher's knowledge, establish the researcher's credibility in the field by acknowledging the expertise of others, and position your research within the contribution of the others in the field. Literature reviews also allow the researcher to consider alternate positions as part of good research is to respond to potential criticism of the study within the context of what the research intends to explore.
While there are several essential strategies in conducting a literature review, the one that seems to be universally the top of the list is to think of a literature review like a rocker box. A rocker box is a tool miners use to screen for gold. As the name implies, once the modern gold miner has pinpointed potential gold sites, they turn to what seems to be a very low tech process. The box has short depth, a screen filter on the bottom, and is usually a few feet in length. The miner shovels dirt onto the screen, and the box is shaken while water runs across the top. The debris falls through the screen, leaving the gold.
Modern research relies on the internet, and the internet is a deep, vast, and somewhat unfathomable source of research material. The researcher's job is to find the most relevant, credible, and up-to-date research available on the research topic. This means you will have to sort through a lot of researcher debris to find the nuggets of gold supporting the thesis! Some more modern tools have not replaced the rocker box because it relies on the miner's experience and knowledge to sort through the mud, sediment, and silt to sort the real gold from the fool's gold.
The best strategy is to set your screens on the research rocker box to filter out the debris of not relevant, credible, or as up-to-date as the research requires. The key is not to make your screen narrow when you begin your literature review; a too-thin screen will sort out useful material—too wide of a net and too much junk research filters through.
A simple way to do this is to rate the literature for review with your topic's relevance. Some researchers use a five-point rating system, with five being the most relevant and one the least. The rating aims to shake out the less than three and leave the three and greater. However, don't simply discard the debris filtering through the screen. While you may not be able to use it in support of your thesis, the material that falls through the screen may have an alternate use. For example, demonstrating some arguments contradict the research's main thrust that may not be credible or well supported.
One side note that many researchers neglect. Even though the internet is more accessible and allows researchers to access materials that are not available from local sources, libraries are still a great source of materials. Don't just assume the internet is the only source for excellent materials!