We were there May 26, 27 and 28 a Thursday, Friday and Saturday and Memorial Day Weekend. I wanted to second the thought to do rides on weekdays and shows and parades on weekends. Also, get to the park when it opens and ride lots of rides in a row. We could do more rides in the first hour than we could all the rest of the day. We usually go from opening until about 11:30am when the lines start to get longer and then go back to the room for lunch and a little lay down. If you dont want to go back to your room take a ride a few times around on the railroad, go watch a show, or do a little shopping. Then it usually slows down around 1pm or so as people take lunch breaks and start getting spots for the parade at 4pm (if there is one).
The most important thing I learned from these boards for using my time wisely was to get another Fast Pass as soon as the first one comes due. Go get another FP BEFORE you go use the one you already have.
Saturday was crazy with people, and huge groups of them too. I was amazed at the larger families (many of them hispanic) that were all there together, that must have cost a small fortune! But they would have grandma wait in line and then go do other stuff until she got close to the front and then all show up, which was frustrating for the rest of us (kinda their own little fast pass!) You might also consider doing DCA on the weekend day as it does not generally get near as crowded as DL.
Also watch the parades, fireworks, and Fantasmic once and unless you love it and HAVE to see it again, consider using that time to hit rides as the lines will
be much, much smaller. The time leading up to these big events will also be very short lines as everyone else will be sitting on a curb waiting for them to start. However, pick a part of the park and stay there, do NOT try to cross over the hub during this time as you will be swallowed alive...lol. And remember that Toon Town closes for the fireworks and does not reopen, and Fantasyland closes an hour before the fireworks and then reopens afterwards. So Tomorrowland is a great place to hang out during the parade and fireworks, or choose Frontierland/Adventureland/Critter Country during the parade (but avoid during Fantasmic times).
Get there early ready to ride the popular rides and use FP's well and you will do fine, no matter how many people are in the park.