It can be difficult in water so clear you can see 30' deep. We always tried to fish an inlet or outlet if the lake had one. We also used long leaders (14-16') were not uncommon. You also need to watch the fish. Not just to see the fish rise, but to try and determine if the fish is cruising the water. If they are you can cast your fly out ahead of where you think the fish is going and just let it set. Fishing dries in alpine lakes can be a blast right after ice out, and it can be very frustrating once they have wised up and seen a few anglers.