Write it down , and then print it out . Begin by recording what you know already, and build on that. Don’t be afraid that some parts of it are incomplete - realize that building an opening repertoire is a long term goal As Mark Dvoretsky explained in Opening Preparation – openings you play should: Fit your style (open vs. closed positions) Fit your memory’s abilities . Relatively speaking, some openings require understanding of plans (e.g. Closed Sicilian), while others, such as King’s Indian defence require remembering a lot of theory as well Don’t easily give up on lines that did not work out in a game, instead try to understand what particular mistake caused a defeat. That being said, if you keep having bad results in an opening – it’s worth reviewing whether it matches your style (see above). It’s may sound obvious, but review it against books like MCO or NCO , computer databases, etc. Pa...