Shooting drills (adapted from "tal" on GotSoccer)
Find a fence or backstop to set the goal up in front of so you don't spend all your time chasing balls. You also need to have about ten balls to work with (all properly inflated).

To start:
Have the shooter standing about 20 yards out from the goal. Have a ball server standing behind and to the right side of the shooter. As the shooter starts to run, serve a rolling ball for the shooter to run onto and shoot. Ideally, the shooter is 10-15 yards from the goal when they shoot. Also, ideally, you'll have a keeper (mom's and dad's work fine for younger shooters) standing in the goal. The shooter shoots for accuracy (i.e., just inside the post on either side). Do this 3 times 10 balls with the right foot then repeat with the left foot. 

Change the drill by having the server stand in front of the shooter and to one side. The server is now cutting the ball back to the shooter who is running on to it. Accuracy of shot placement is again the objective. Do this 3 times 10 balls with each foot. 
At this point you've taken 120 shots on goal.

You can take this drill to the next level by serving a bouncing ball to the shooter.
Finally, you can serve square balls from either side. These are the hardest and should come last.

If you are good enough to serve the ball consistently with your foot great. If not, serve it from your hand. Either way you need to consistently serve a ball that is correctly paced and accurately delivered.

Important:
These drills (or any others for that matter) should be set to the level of the player. A good rule of thumb is that the player should be successfully hitting the target at least 50% of the time before you increase either the speed of service or difficulty of the drill.