CIHR discusses general steps in a synthesis in "A Guide to Knowledge Synthesis". Most methods use some combination of these steps, whether they are linear or iterative, and whether they deal with qualitative or quantitative or mixed studies.
Remember, each method will have its own requirements and processes.
1.Defining research question/ objectives
2.Defining eligibility criteria (inclusion/ exclusion)
3.Identifying potentially qualifying research (searching)
4.Applying eligibility criteria (screening)
5.Collecting data
6. Quality/ critical appraisal
7.Data analysis and interpretation
