How to Spend Your Time in Denali National Park and Preserve
You can do a bus tour of the park in a single day. Allow for all day, and try to go at least as far as Eielson Visitor Center. If you can, go out to Wonder Lake. A few buses go a few miles farther to Kantishna, but the views from Wonder Lake are better; there's no reason to go those last miles unless you're staying at one of the inholding lodges.
If you have more than a single day, the best thing to do is camp in the park. The longer you stay deeper in the park, the better chance you'll have of seeing Denali, which, on average, is only visible one day out of three. Again, Wonder Lake is the spot of choice.
It's also easy to fill a day around the park entrance, taking rafting trips on the Nenana River or going on some of the short hikes near the visitor center.