Here's a good foundation drill to work front crosses and serpentines:
Set up two jumps in sequence about 15 feet apart. With your dog on your left, run from jump #1 to jump #2, slowing up right before jump #2 to cue a turn. Turn towards the dog and now he's on your right. Run towards jump #1, slowing up to cue the turn, and turn towards the dog.
For serpentines, turn the jumps so they are parallel to each other. Set the dog up with his left shoulder just about at the jump bar. On the opposite side of the jump and with your left arm cuing the jump, release the dog. Switch to your right arm and indicate jump #2.