In a nutshell, note-taking and experience are key to repeatable results. Anyone can get lucky occasionally but repeatable results under varying light conditions are the objective. Not all center-weighted meters are the same; some are 80/20 (Nikon F3) while many are 60/40 so knowing your meter is important. If the scene permits, try approaching a particular portion of the scene to essentailly spot-meter it and only it before making exposure adjustments and returning to original vantage point for framing.