One of the simple principles on defense is to get your hands up. If five players have their hands up they take up a lot more room on the court than with their hands down. The measure we use on our team is that if you are off the ball on defense, your hands have to be as high as your shoulders. Even with bent arms this gives the defense an advantage. Having your hands up on defense isn’t just good for taking up space. Having your hands up on defense allows your team to make the defense look more imposing than it might actually be. When a team comes down and sees five defenders with their hands up, they are less likely to be aggressive in their attack and will most likely play further away from the hoop. As teams do this they are decreasing the likelihood of them scoring because they are moving away from the hoop and thus into lower shooting percentage territory. The other advantage of having hands up is that your team is ready to react to a pass. With their hands already up players don’t have to lunge for a pass, their hands are already there. If their hands aren’t there then there is no steal possible.
When I first started coaching I put a huge amount of emphasis on players getting their hands up when they are off the ball. I told my team that if they had their hand in the passing lane (the line directly between the passer and the receiver) at some point (and probably frequently) someone would literally pass the ball right to their extended hand. When my team started seeing this come true they looked at me like I had performed a magic trick or had powers of divination. They bought in quickly and even my less athletic players felt they could contribute defensively by effectively denying the person they were guarding simply by raising their hands into the passing lane.
When trying to teach off the ball defenders to keep their hands up the key is giving them measuring sticks so they can evaluate their behaviors. The first measuring stick I have already given: players hands should be as high as their shoulders. The second measuring stick was where to put their body. For a defense that forces teams into your interior (as I have run at times), I had players mentally draw a direct line between their man and the ball and put their inside hand (the one closest to the ball) half way on that line, with their head looking out at their hand so that they can see in the peripheral both the person they are guarding and the ball. As the player they are guarding moved, they have to keep that distance between ball and the person they are guarding. Small adjustments like getting your hands up off the ball on defense don’t seem like a magic cure for an ailing defense but it is this attention to detail that will gain you extra possessions and lower your opposition’s shooting percentage.