Critical appraisal is the method by which you can assess research for its reliability, relevance and results (the 3Rs).
Often, critical appraisal is taught as though it should be a careful examination of a research paper: given the fact that no one has the time for this careful examination, and it just isn’t feasible, given the sheer amount of research that is published each day, then the answer has to be, know your biases – really well -and then apply them in a more systematic speedy way.
Wikipedia therefore offers a neat option to read about and learn some more about this stuff, but the question is what’s in there and how much of appraisal does it cover?
Overall, my assessment is there are some appraisal nerds out there doing a good job. In terms of what to have a look at:
The page on randomized controlled trials is pretty comprehensive and includes a section on randomization procedures, allocation concealment.
A Blind experiment page explains single, double and even triple blinding.
Overall Wikipedia – not bad.