I would agree with the others: 2 days, or even 3 days, are better, if you can swing it.
However, if your schedule is so limited that you can't swing more than 1 day, you can still have fun. Here's how I would do it.
Stay onsite at RPH the night before. Make sure to print out your Universal Express passes. Get up for early entry to WWoHP at IoA. Run to WWoHP, see Ollivander's Show, then go to Forbidden Journey and Dragon's Challenge. Flight of the Hippogriff if you just want to be complete (it's not that exciting a ride). Grab a butterbeer at the Hog's Head if your'e so inclined. Move into Jurassic Park and do the water ride. The go down into Superhero Island and hit Spiderman and the Hulk Coaster. Circle around into the Seuss land and go on Cat in the Hat. Circle back to Mythos for lunch. Yes, I know this seems like a lot of rides before lunch, but with Universal Express it is doable.
After lunch, head over to USO. Ride Rip Ride Rockitt, Transformers and the Mummy. Then head around to Men In Black, the Simpsons Ride and (if it interests you) Kodos & Kang. Check the daily schedule, and go to Despicable Me and Shrek 4-D, ensuring that you make a Terminator 2D/3D show.
After this, depending on how tired you are, you could try to fit in Disaster or Twister, or (my preferred choice) the Horror Makeup show. If you want to head back to IoA, the Jurassic Park 'Exhibitor's Center is a fun place to hang out.
The key to all of this is being there early and having Universal Express for everything but Forbidden Journey/Ollivander's. Universal Express isn't a walk-on, but it will significantly shorten your waits. Even in the busiest summer times, we have never waited more than a few minutes for anything with Universal Express.