Last time I was at Sturgis was 1994, we stayed at the Rapid City KOA. My parents had their 5th wheel (and our two kids), the wife and I had a tent. The campground was overcrowded. It was damn near impossible to take a shower or do laundry, there were that many people there. I would hope they learned from that and didn't cram the place beyond full, in the subsequent years. We stayed for five days, and barely scratched the surface of things to do and places to see. I want to go back, perhaps when I retire for the second time....

If you don't mind breaking camp once or twice: Spend the first night at Devil's Tower. IIRC there are a couple campgrounds at the entrance (IIRC they show 'Close Encounters of the Third Kind' at the KOA at nights). Devil's Tower is a must see. But that's about it, once you've seen it, it's time to go (sorta like Niagra Falls, IMO). The ride to it is long and boring, IMO, if you're coming directly from Sturgis.

Find a campground around Deadwood/Lead and spend one or two nights there. Deadwood gets packed with bikers, the bars are full, the slots are fun, there's a bit of history to explore. We had a good time there. You could make this area your 'base of operation', or move on down to Keystone, Rapid City, or Sturgis for the rest of your stay.

The town of Sturgis is maybe a day's worth of looking over. Lots of vendors, etc. Even more people watching. Pack a good pair of walking shoes or boots. It is a good central location for the vast amounts of territory you can explore.

Decent rides:
Spearfish Canyon
Badlands (bring water-it's like a sauna in there) and Wall Drug (just because)
Custer State Park

Must Sees:
Mt. Rushmore (ya gotta go during the day, and at night)
Crazy Horse (do Rushmore/Crazy Horse/Custer/Rushmore the same day-and you're good)

Bring warm clothing. It gets chilly at night. And it get's dark, really dark at night. I rode back from Rushmore at 1am, in a dense fog, so be prepared for anything.

 

definitely be prepared for anything, weather-wise. this year, everyone was wearing sweatshirts and jackets for the first few days. then it was nice and warm for a few days, then it rained buckets and hailed.

also take earplugs, especially if you're camping.
and when you go down to custer state park and mt rushmore, there's a road (i think its called iron mountain, or something like that) which is a great ride.