What I mean by "level" is to strive to take a level classic pool stroke as often as possible. Please note that the pool pros hardly ever employ a non-level address or stroke, even if using extreme amounts of ball spin or english.
Think "I need to make a level stroke for most shots" and not a "I need a straight stroke". Most every pool stroke is aimed as a straight stroke, but it is the near-level cue stick that will yield terrific, positive results, reducing curve action on english strokes and more. (Bear in mind, I say "near level" as most shots are taken over an interfering rail.)
In my own game, I recognize that even when quite low down on the cue ball for a stroke, my cue still appears to be straight, as resembling the position at center ball address. For specialty shots such as I discuss elsewhere on this site, adjustments are made off-level.
Avoid jerky, choppy hand movement and build level, even movement. Watch your percentages soar. And if you are still struggling with your stroke, close in your bridge hand so that is a few inches closer to the balls also.
