Practice More
Think about how you feel during practice. Relaxed, right? Well, that's why practice is the best place to start dealing with your slump. In practice you don't have to worry about your opposition, or losing the game. You can just practice.
So, focus on grooving your shot. Start close to the basket to build your confidence, and then slowly move back a bit at a time.
The more shots you make, the faster you're going to get out of your slump. So, practice, practice, practice.
Clear Your Mind
The more you focus on the fact that you're in a slump, the more slumpy you'll be. So, it's important to learn how to clear your mind.
You can try this useful technique for clearing your mind:
•Start by shooting five balls eight feet away from the hoop.
•Next, take five shots using your weaker hand.
•Now, go to the free-throw line. Shoot another five shots with your weaker hand.
•Go to the 3-point line. Do another five shots with your weaker hand.
•Now move over to half court. Take five shots with your stronger hand.
•Don't laugh, but now you're going to stand on one leg. Take five shots with your strong hand. Make sure you focus; really try to make the shots.
•Don't move. Now, close one eye, and keep standing on one leg. Take 5 shots with your strong hand. You might not make it, but that's not important. Just keep trying.
•Now, switch to your weaker hand. Stay on one leg, with one eye closed. This is going to be hard, but again, really try to make it!
•Now move into your regular shooting range and do some jump shots with your right hand. Don't worry about making or missing them. Just shoot. These shots are really easy now, right?
If you make a shot, then make sure you congratulate yourself. Don't berate yourself if you miss; just focus on the good. And remember to have fun!
If you're in a slump, do this exercise as often as you can. The good news is that once is usually all it takes!
Source: http://www.ihoops.com/practice-time/shooting/3-ways-to-escape-a-shooting-slump.htm