I recommend this book, which goes into the details of compositing from the perspective of someone doing the work daily on high-end feature films:
Thanks for the book recommendation will check that out.
Yes I know I have a lot of good answers from people already just seeing what else I may get that has not already been said from different sources.
I hate to say it but just being a worker bee in the visual effects industry is a lousy way to make a living. There are 14 year old kids that have figured out the software enough to do some pretty amazing things. The industry is filled with technicians with a boat load of skill and experience that are looking for work.
If you want to succeed you need to first of all know how to run a business. I know some brilliant artists that have been broke their entire life because they never learned how to run a business.
Secondly, you must have strong creative skills that can mesh with others. The only real money to be made in this field is made by being an outstanding designer. To do that you need to study art, literature, history and know a bunch about psychology. Just pulling a good key or being able to rotoscope an image will not guarantee you a job that will pay the bills for a single person living in a small apartment. You must push yourself to excel.