One of the biggest problems that basketball players have with ball handling is that they are constantly looking down at the ball. In doing so, they are missing all that is going on around them on the court. A missed pass for an open layup or jumper can mean the difference in the game. That is why guys that are good at handling the ball are always looking up. Consequently, they are able to make the correct decisions with the basketball during the course of the game.
A ball handling drill that can be used during your basketball training to help keep your head up is dribbling a basketball while tossing a tennis ball to yourself and catching it. This drill requires extreme concentration and focus on the tennis ball in order to catch it, so there is no way that you can look down at the basketball while you are dribbling it. Start this ball handling drill off by simply standing in place, pounding the basketball with one hand, and tossing the tennis ball up and catching it with the other. The next step would be to add a change of direction dribble (ie. a crossover, between the legs, behind the back, etc.). So stay in one spot, toss the tennis ball up, do a crossover dribble, and catch the tennis ball with the other hand. The third step after you have mastered the first two would be to add movement. Going full court using a zig zag pattern dribble the basketball and when you change direction with the basketball, toss the tennis ball up and catch it with the other hand. You can and should use all your change of direction moves with these drills. The final two steps would be to add double moves (double crossover, behind the back crossover, behind the back between the legs, double between the legs, etc.), and then double moves with movement.
These final three steps can be seen in the video below where the player is first going full court zig zag with a single move while tossing the tennis ball to himself. Then he does a stationary double between the legs while tossing and catching the tennis ball. Finally, he does the double between the legs move while dribbling full court.