The fit between the neck and body of your saxophone has a HUGE impact on how it feels to play.  Problems with the neck fit will often show up as sluggish response, difficult intonation, and sometimes even splitting or warbling notes.  Your neck's tenon should slide smoothly into its receiver with a slight resistance and be completely air tight once installed.  The neck should not rock up and down, even before you tighten the screw.  The neck screw will then only need to be turned slightly to stop the neck from spinning in its socket.  Depending on how dire the situation is to begin with, this work can completely change the character of a horn for the better - making an average horn good, and a good horn great.  Bring your horn in and we can check the neck's fit and seal to determine if this type of work would be beneficial.

It goes without saying that any pad leaks will greatly reduce the effectiveness of a good neck fit, so these issues will always be attended to first.