DISclaimer: this post is not intended to be sarcastic or arguementative in any way.
I would suggest starting to get FP's for the major attractions almost immediately upon entry to the park...even if it doesn't seem particularly busy when you first get there, it doesn't take long for the lines to start to build(during busy times)....If you do this, you can get in quite a few attractions using the standby lines and then when lines start building, you'll have the FP to use...