Where to cast?
When you are casting the dry fly you will probably be approaching from downstream. You will need to cast upstream or up and across as you work from the lower part of the hole toward the top where the water is pouring in. Be looking for rocks that break the current or that are under cut to give a fish a place to hide. There may be seams of faster water and slight breaks in the current that will provide a resting place for the fish. They will be resting in the slower parts and waiting for the current to bring some morsel of food right by them. Your goal is to get that fly to hit just along the outside edge of the faster water and you will need to mend line properly as the current brings the fly back downstream. It is very important to be on top of this mending situation so that slack does not form and cause you to miss strikes or cause drag on the fly.
If you are fishing nymphs, you will cast up and across but you will need to get the flyline above the water so it will slow down and give the fish a natural look as it comes by them. As you get to the upper reaches of a hole, you will only need to cast the fly far enough to get most of the leader under water. Try to keep the flyline completely out (4-6in. above the water)so that there is no drag placed upon your line.This will be the way that you will do most of your early season fishing. Good luck and let us know how you fare.