Defense is all about helping. No one can guard a good dribbler, You have to walk kids through how to help and then how to help the helper. But in order to be helped, your team needs to work as one unit and not as a group of individuals. Everybody has to follow the same rules, so they can read one another and to know where and when to help. 

Here are some simple defensive rules that can be applied in all situations. 

If we need to defend the point, we need to know who are we dealing with. Defending the point is the hardest thing in basketball, because the offense can see everything and can use full court. The two things your player needs to do are: 

1. cut off the strong side and try to make him dribble with weaker hand and go weak side

2. protect the paint 

In the situation where your player needs to defend the wing position, also there are two rules:

1. no middle

2. no paint

Everybody knows that the majority of time your players will spend distant from the players that they guard. So, many times they will need to closeout, and how this action can be tricky and if not done right the attacker can drive by you very easy. This is how it's done properly. 

2/3 of the distance between the defensive and the offensive player, the defensive player needs to sprint, and on that 2/3 spot he needs to go in the defensive stance, make small steps as he slow down, and put his hands up so he would confuse offense. 

Lets see the video: