Methods for reducing bias and error (Littell, n.d.):
Develop and publish a protocol before beginning the review
Create explicitly eligibility criteria
Use a variety of search terms and databases to find studies potentially eligible for inclusion
Search for grey literature
Request missing data from primary study authors
Use structured screening, data extraction, and coding forms
Conduct screening, extraction, and coding in duplicate and resolve discrepancies
Assess risk of bias including risks of publication bias and reporting bias
Use meta-analysis if possible (if 2 or more studies provide quantitative data on parallel constructs)
Document methods and decisions in sufficient detail for replication