Having undertaken the literature searches, you will then be in a position to screen the results and select the studies for your systematic review based on the inclusion/exclusion criteria that you developed as part of your review protocol.
There are a number of steps to screening your results:
Sometimes, steps 1 and 2 can be combined if time is at a premium. The vast majority of articles will probably be excluded in steps 1 and 2, so that the final step is to find the full-text of the articles that are in your 'Include' set and then read each one to identify whether they should be included or excluded.
To prevent selection bias, screening should ideally be undertaken independently by two reviewers with a third reviewer to resolve any conflicts. You may find it helpful to undertake some preliminary/test screening of a selection of studies to ensure there is agreement amongst all reviewers on the application of the inclusion/exclusion criteria.
It's useful to keep a record of the reason why specific studies have been excluded from your review at the full-text screening stage - this is where systematic review software can help with this process. See the 'Systematic review software' page for details of different packages that are available.
This is the first part of a Cochrane Learning Live webinar from the Qualitative Evidence Synthesis series on Selecting studies and assessing methodological limitations by Professor Andrew Booth, Professor in Evidence Synthesis at University of Sheffield and Professor Jane Noyes, Professor in Health and Social Services Research, Bangor University.