Solid basketball defense is a necessity for any team vying for a championship, and you want to have a variety of defensive strategies so you can handle a variety of situations (see my thoughts on reasons to run a full-court press). The best offense in the league won't be enough if you can't get the ball. Look at the Lakers in the 80s - Showtime! Magic leading the break, Worthy streaking down the side for a long armed authoritative dunk. And if they needed to set up an offense, they had Kareem inside shooting his unstoppable sky hook, and Michael Cooper on the outside popping threes. They redefined the game of basketball into a fast breaking, high scoring steamroller.
But without solid basketball defense, they wouldn't have been able to get the break started. So it was a good thing that they had one of the best defensive players in the league in Michael Cooper. And one of the scrappiest players in the league in Kurt Rambis, as well as the height of Kareem to rebound. Spectacular offense scored them many points, but it was solid defense that kept the other team from scoring more.
I always focus on defense at the beginning of the pre-season. Defense and conditioning, since they go hand in hand. Players need to get the ball before they can do anything with it - the better their defense is, the more often they'll find themselves in possession of the ball. And keep in mind that even at the professional level, the average shooting percentage is under 45% - greater than half of all shots that go up, miss. If your players can rebound on the defensive end, they cut down the ability of their opponents to score.
Of course, if your players can't play defense, if they are slow to transition from offense to defense, you can expect the opposition's shooting average to skyrocket as they stroll past your players on the way to the hoop. So here's some ways you can set up your defense to stop your opponents and give the ball back to your team.
Every player needs to know how to play man to man defense. Man to man is a basic skill that needs to be taught and learned, because a player that can't play decent man to man will be a black hole on the floor - and your opponent will find that black hole and drive through it all night. So start off the season by teaching solid man to man principles, as well as how this integrates into a whole-team concept with elements like help and recover.
One important aspect of any basketball defense, whether man to man or zone, is quickness. Push your players to improve their quickness, and they'll improve their effectiveness at both ends of the court. Run agility drills and sport-specific speed drills, and you might want to check out some stand-alone, third party speed-training programs that focus on quickness - they aren't easy to find, but the one in this link is pretty solid with lots of good reviews.
Not that you need to play man to man all the time. Personally, I prefer man to man over zone, but there isn't anything wrong with mixing it up every now and again. Use a zone sometimes if you want - the 2-3 Zone and 1-3-1 Zone are probably the most commonly used zone defenses and they have their place among a team's defensive strategies.
Just don't let your players think that playing zone is easier and less tiring than man to man, because once they start thinking that, they start acting like that, and that's when holes in your defense start to open up. Good zone defense requires strong man to man skills and excellent communication among players, and defenders need to see the court and be able to plug holes immediately. Playing a good zone defense is not easy.
For a good look at how to build a strong, team-oriented basketball defense, drills included, you can't get much better than the legendary DeMatha High School, which has produced plenty of championship teams built on their excellent defense. DeMatha head coach Mike Jones teaches their defensive strategies in Building the DeMatha Team Defense - an excellent instructional DVD to add to your library.
Of course, basketball defense can start anywhere on the court - most "normal" game situations have the defense setting up in the quarter of the court, defending their own basket. But we can also extend that to the half court and to the full court - in other words, we can apply more pressure (presses) and try to force turnovers by using a Half-Court Press and/or a Full Court Press. These defenses would be used for a few minutes to force a couple of turnovers, then taken off so that the offense doesn't adjust to them. Then they can be used again later in the game.
One option that bridges man to man defense and a full court or three-quarter court press would be the Run and Jump - an explosive defense aimed at creating panic in your opponent and hopefully turnovers.
And of course there are several basketball defenses that combine man to man with zone elements, to get the strengths of each while limiting the weaknesses of each. These would be defenses like the Box and 1, the Triangle and 2, and the Box and None - all good defensive strategies under the right circumstances.
Choose the basketball defense that best suits your personnel - a smaller, quick team would likely be more suited to straight up man to man to take advantage of their speed, while a bigger, slower team would likely be more suited to a zone that could take advantage of their height.
But you should also have a few alternative defenses under your belt - if you play the same defense for the entire game, you run the risk of your opponent figuring out how to beat it. Having the capability to change up your defense from time to time will force your opponent to constantly adjust. And having a good press to throw at your opponent every now and then is usually good for a few quick baskets.
Regardless of the style of defense you choose to use, instill in your players the idea that they must be offensive on defense - they cannot allow the opponent to dictate what happens.
They must also transition quickly from offense to defense (use this drill to improve transition from offense to defense)
Their defense must control the game - they must direct the ball in the direction they want; they must apply pressure to the ball carrier so that he makes weak or ill-timed passes, or takes poor-percentage shots. They must force the opponent to either turn over the ball or take a shot they don't want.
And that happens when you play great basketball defense.