Word of advice, don't try to kill your velocity too high up by only burning retrograde. If you're coming in short of your target, angle the craft so the engine is thrusting a little downwards, it helps kill vertical velocity so you go farther and actually make it to your target. That works best in realistic mode, for normal I always found it most effective to just have a nice TWR on my lander and kill all my horizontal velocity right over my target.