Find a brick wall - most schools have them. Franklin courtyard is ideal. Brick walls are better than smooth concrete walls because of added dimension of occasional unpredictable return. Pitch-backs are ok but limiting. Brick walls are best.
Start close - about 10 feet away, with your dominant hand, pick a spot about 8' high on the wall and see how many times in a row you can hit that spot and catch the return without dropping. Throw with enough force to make the ball go in a straight line.
Progress to using other (non-dominant) side. Repeat step 2.
Get a friend and invent competitions
Throw right catch left - throw left catch right - repeat
Catch and face dodge
Catch and split dodge
Catch, throw a fake pass, then side arm pass
Throw off-hand, i.e. if you're a righty, with hands positioned for a right handed throw, put the stick on the left side of your body and throw/catch from there. Repeat with non-dominant grip from the other side.
Use one hand only on the stick to catch and throw (builds wrist and forearm)
Do 'quick-stick', i.e. no cradle catch and throw - as soon as the ball hits the net make a throw
Typewriter: Shuffle left while throwing and catching, then shuffle back right while catching and throwing - repeat
Move farther from the wall, pick a target a little higher up, repeat all of the above and see how good you can get at not missing while progressively getting further from the wall
Play Pig/Horse with a friend - pick bricks on the wall to hit.
Invent your own drills!
Perform this routine 4 to 5 times a week for 15 to 20 minutes and your stick skills will improve a great deal in a very short period of time. You will be amazed!
Crank up your stereo or headphones and have some fun!