Thanks to the DIS, we didn't make a lot of mistakes, but there were a few.
With a group of seven, we foolishly tried to do mid day breaks, which totally didn't work for us. We used more energy, and wasted more time trying to take a break than it was worth. After about the second day, I gave up on that, and from that point on, we have never bothered with breaks.
We meandered into AK at about 10:00 in the morning on a day when the park had AM EMH. It was a DISASTER! We then wasted the better part of an hour waiting for my cousin to pick out a pair of flip flops to buy because she had a hole in hers (the hole was there before we left NY to go to Florida, why she didn't just buy a new pair in NY I don't know). By the time we got started in the park, we managed the Safari, and walked one of the forest trails, then it started pouring, so we headed for lunch, and wound up sitting outside in the rain to eat. We went to see Rafikis Planet Watch, and the Conservation Station, and that was pretty much all we got done the whole day.
The first year we didn't really understand that you can use fast passes after the ride window has expired, so we rushed back and forth across the park to use our FP's during their window, and ones that we weren't able to get to in time we didn't use. It was on day 5 of our 7 day trip that it finally dawned on me that I had read here you could use them late, so we tried on TT, and sure enough they were accepted. That made the last two days, and our entire next trip a lot easier on our feet.