This thread helped me understand TFE back when I was studying. It goes over what all the lines and shapes mean.
http://forums.studentdoctor.net/threads/my-wicked-sick-pat-tutorial.528643/
The general strategy I use is to find something unique about the two sides presented (such as a hole that goes all the way through the shape), then determine what the unique feature would look like in the missing view. If an answer choice doesn't match up with what you think it should be, eliminate it. Then again find another unique feature, compare it against the answer choices, and eliminate the ones that don't match. Repeat until you only have one answer left, because that is the correct answer.
Also, the thread I linked to talks about a strategy called line counting. I recommend you do not rely on or use this method since the ADA has caught onto that trick a while back and now makes their TFE questions immune to line counting.