Don't have any 'sites to recommend, but a few suggestions:

1. Practice, practice, practice and then practice some more; the beauty of digital is that the film is cheap!

2. Shoot, review, adjust, shoot, review... you get the picture.

3. While you're practicing, I suggest trying the following:

a. Set your camera to shutter priority and then set your shutter speed to 1/500th of a second (as you become more familiar with the lens, you can dial this down a bit)

b. Set your focusing to that it's only usuing a single point, and ALWAYS pay attention to where the camera is focusing and adjust as required

c. Understand the DoF of this lens; remember, long focal lengths have much shallower depths of field at a given aperture then shorter focal lengths.

Good luck!