Brian has said it all...very well put :). Of course i will add my .02 from my experience. Make sure you have some broad shoulders and a good knowledge of pretty much EVERY aspect of your system. I am sure that many will agree that when the backups are slow, or applications are running poorly, or networks are running slow, etc... the first stop it appears for EVERY one is the DBA(they will come to you with the problem because data is high on the list). Not only will your prove your data is or is not the problem but your input is quite often wanted for the repair EVEN if its not your field of expertise. Like I was saying Brian is right on the numbers with everything he's quoted..print it and use it as a guideline now and later in your career.

Good Luck

-D-