You mentioned in one post about targetting 300 fpm descent on final. That's a new one for me. Your aim point and airspeed are the most important items when on final.
Jas is right - in 14 years of flying I've never targetting a certain descent rate during a visual approach to landing (an instrument approach is a bit different - but you'll get to that later). Get your aim point right and control the airspeed with power. There are too many variables to worry about a target rate of descent.