Before you begin a systematic review, you should decide who is going to be included in the review process. Systematic reviews intended for publication should involve a librarian in the formulation of the search strategy.
You should document at the time all of the steps that you take to complete your review, as this allows your methodology to be accurately compiled.
To reduce bias in a systematic review, it is important to develop a review plan or protocol.
Using a protocol to plan a systematic review:
A protocol should be developed using the PICO/PICo framework to determine the parameters of the systematic review. Eligibility criteria such as publication type, publication date, language and age of subjects should be specified in your protocol. It is important that inclusion/exclusion criteria are also determined before beginning the review, as the inclusion or exclusion of studies determines the scope and validity of systematic review results. It is recommended that you read this article: Selecting studies for systematic review: Inclusion and exclusion criteria.
You may wish to register your protocol in a publicly accessible way. This will help avoid other people completing a review on your topic. Similarly, before you start doing a systematic review, it is worth checking that nobody else has already registered a protocol on the same topic.
If you intend publishing a systematic review in the health sciences, then it should conform to the IOM Standards for Systematic Reviews.
If you intend publishing a systematic review in the Cochrane Database of Systematic Reviews, then it should conform to the Methodological Expectations in Cochrane Intervention Reviews (MECIR).