Here is a drill to develop an athletes defensive slide or sometimes called lateral shuffle. What I like about this drill is that it is competitive and reactive. All this means is that the athletes are competing against each other and that they must react to each others movements. Most athletes will work harder if there is competition involved.
I generally do this drill going from baseline to foul line. There are two lines of players starting on the baseline where one line is offense and one is defense or shadowing the movement of the offensive player. I will generally do a work period of 10-15s, with 60-90s rest. I will commonly use 12-16 players in one large group, so that they get the required rest. This is a drill that requires maximum effort and should only be performed after a thorough warm up. Even though I am using it with a basketball team, it can be implemented in any sport training program that requires lateral movements.