When appraising evidence at any level--but particularly those on the lower half of the 4s Pyramid--you must ask questions to determine the usefulness of the evidence, particularly in terms of validity and importance.
Is the Study Valid?
Is there a clear, defined research question?
Was the study "blinded"?
Was the test evaluated?
Are the methods clear?
Is the study reproducible?
What were the outcome measures?
Are studies consistent in systematic review?
Are the Results Important?
Is the evidence relevant to your question?
Is the methods section clear?
In a systematic review, are individual studies considered for validity?