Another vote for focusing on the ball all the way into the contact point. Visualize the contact point and have the picture in your mind of how your racquet is going to rip through that spot.
I frame it when I swing too early. Even when someone is hitting big if you're split stepping and watching the ball off the racquet you can get to most balls with enough time to set-up. I tend to pull the trigger a bit too soon when I see the ball coming fast, even though I'm set-up (lack of talent showing through).
This happens even more when my opponent is hitting big and varying the spin (so some balls kick up and others skid more). The pace steals time and the different bounces make for last minute adjustments.