Read the theory thoroughly as it is stated in your primary research material. If you are examining a theory conveyed to you by a medium other than written text, such as theories behind a speech in a film or television performance, try to discern some of the major specific ideas behind the theory.
Research the major ideas behind the theory. Encyclopedic research is a good place to start, as it will give you the information concerning the idea in a concise and unbiased way. You should also consider doing external research into contrasting ideas, or iterations of the ideas within the theory in question. This will allow you to see the ideas from multiple perspectives without the possible bias in the original theory.
Form your own perspective on the ideas, based on the broader understanding you achieve through research. This will give you a personal understanding of the theory in question. You may often find that theories use obscure language, including jargon. This is especially true in theories presented to a wide audience. By abstracting the ideas from the language and construction of the overall theory, you will be able to better look at the true implications of the ideas.
Arrange the theory into a simplified argument to further help you abstract its ideas. Any theory can be deductively examined by extracting its simplified versions. By extracting these into simplified arguments that implicate a simplified conclusion, you can look at the validity and soundness of the arguments made by the theory.