Oh there are lots of little things to know/discover about Universal, but then telling all of them to you would ruin your opportunity to discover them for yourself. Also, the things I like, might not be the things you like.
1. DO take time to look at the details. Details like the topiary in Seussland are amazing.
2. We love the onsite deluxe hotels with Express Pass, but Sapphire Falls is really nice.
3. DO take the shuttle boats to the hotels.
4. You can eat pretty inexpensively if you are so-inclined. One hidden food gem is the pulled chicken salad at the Three Broomsticks. The "Feast!" is okay, but the pulled chicken salad is a gem. Look for it on the 2nd menu they have at the register. Another gem is the bangers and mash at the leaky cauldron. Bangers =(English) sausage. It comes with mashed potato, sautéed onions and cabbage, minted peas, and roasted tomatoes. Everything is delicious.
5. Butterbeer is very sweet, but Diagon Alley's Hopping Pot has a fizzy orange juice that is tasty. (It is sweeter than plain orange juice, but not cloyingly sweet.)
6. When you are in the MIB pre-show, pay attention to the advice you're given. DON'T be a DUFUS!* (*You'll comprehend this statement when you see the pre-show.)
7. DO see the animal show.
8. As others have said, even if you don't all ride, everyone can see the queues. Also, don't be afraid to split up a bit. There's often an outdoor entertainment to see while others ride, or a tame attraction is next door to a wilder one.