Redundant or poorly organised reviews waste effort and resources, and add to decision making confusion
You should have a clear idea on what you are question is. Do this before starting to search the literature in earnest to avoid expending unnecessary time and effort.
Discuss with your team or supervisor what exactly you are asking and what the criteria for inclusion and exclusion are.
Consider using the PICO framework to help form your question.
If you are unsure, consider allowing time for a scoping review to establish the research 'landscape'. This can help clarify where to direct your efforts.
A scoping review can be a useful prior stage to a full systematic review. Scoping reviews provide an overview of the literature around a topic. They are typically more broad, but with less depth than a systematic review, and generally do not include any statistical analysis. They can be useful for identifying questions which are suitable for a systematic review.
Systematic reviews are significant undertakings requiring more than a single individual's input. Typically a systematic review team will consist of:
Note. If you are considering undertaking a review as an individual then it is more appropriate to describe your study as a review done in a systematic manner, than a systematic review per se. The same processes should be followed, as all research benefits from a systematic method, but a single researcher cannot eliminate bias from the review process, so cannot meet the standards of a systematic review.
By the end of the planning stage you should have a protocol for your review;
It is a good idea to register your protocol at PROSPERO so other researchers do not inadvertently duplicate your study.