As a reminder, conducting a systematic reivew is very methodical and time consuming. Before starting the process you need to plan out your protocol.
"The preparation of a protocol is an essential component of the systematic review process; it ensures that a systematic review is carefully planned and that what is planned is explicitly documented before the review starts, thus promoting consistent conduct by the review team, accountability, research integrity, and transparency of the eventual completed review. A protocol may also reduce arbitrariness in decision-making when extracting and using data from primary research, since planning provides an opportunity for the review team to anticipate potential problems."
Moher, D., Shamseer, L., Clarke, M., Ghersi, D., Liberati, A., Petticrew, M., … PRISMA-P Group. (2015). Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement. Systematic Reviews, 4(1), 1. http://doi.org/10.1186/2046-4053-4-1
There is a growing movement to standardize the "best practices" in terms of protocol and methodologies for this type of research, and there are a number of bodies are making recommendations. Below are the major organizations to be familiar with. Not sure where to start? Read the Cochrane Handbook, the IOM Report, or the PRISMA Statement.