1. Train the person before you turn them loose.
2. If the person is a rookie or novice, they will probably require extra time and training.
3. Depending on the magnitude of what you are delegating, it may be months before you can turn the person loose on their new assignment. If you are delegating answering the phone properly, this may only take a couple of training sessions. If you are delegating an entire department that is key to the success of your organization, this could take months of training. Don't underestimate or be surprised by the amount of training it may take.
4. Be prepared to see the person fail. Failure is a part of learning. Failure can be frustrating for the person doing the training, but it is a necessary part of developing and delegating.