Agree with the above posters. You can't swallow all of YNP in one meal, but you can get a good feel for areas where you'd like to spend more time on your next visit, and there will be a next time. Some secrets (Don't tell anybody).
Don't forget camera and binoculars. From the west gate to the Grand Loop is 12 miles. Lots of wildlife on that little stretch, so watch for other cars pulled over. There's something to see, or they wouldn't have stopped. There's a Ranger station as you get to the loop. Stop in to see where the animals are that day. They'll know.
The SW quadrant boasts Old Faithful and the geyser basin. Stop in Yellowstone Lodge while there. A beautiful lobby. The SE quadrant has Yellowstone Lake. The NW quadrant has Mammoth Hot Springs. The old Army Barracks are in the small settlement there and elk wander through the streets. The NE quadrant has the upper and lower falls of the Yellowstone River. The lower falls are higher, but farther away from the headwaters - so lower falls.
The Tetons-
Drive the Teton Park Road south from Rt. 191. It passes Jackson Lake. Take Signal Mountain Rd. to the top. There's a viewing platform up there where you can see lots of the park and the Tetons above the tree line. My last visit, a hot air balloon went by - below me.
Then back to the Jenny Lake Loop Rd. Further south, there's a tiny turnout that holds maybe 5 or six cars. Walk over to the shore, sit on a rock and feel your Blood Pressure drop about 20 points. The prettiest view you may ever see.
As long as you're that close, you might as well drive into Jackson. Souvenir shops abound, but the Million Dollar Cowboy Bar is worth a visit. Good burgers, and the stools at the bar are saddles. The park in the center of town has arch entrances at each corner made out of Elk horns.
If you missed something, don't worry. You'll be back.
Retired and visiting as much of this beautiful country as I can.
