Critical appraisal is the assessment of evidence by systematically reviewing its relevance, validity and results to specific situations.
The CASP (Critical Skills Appraisal Programme) website has a useful range of free downloadable resources which can help you structure your research strategy and help you shape your research criteria. The CASP Checklists can help you determine which studies to focus on and which match the criteria you have laid out for your systematic review. The critical appraisal tools are designed to be used when reading research and include the following:
Mixed Methods Tools
These links will direct you to further sources of critical appraisal help
This video presentation from Dr Andrew Booth at ScHARR, University of Sheffield, talks you through the process of critically reading a qualitative study/research paper, using the CASP checklist, with on-screen analysis and highlighting of text.