There will be a ton of stuff to do on Gameday.  As I mentioned earlier, I know that there is a CougarTown Tailgate at the World's Fair Park (walking distance to the stadium).  It is also realatively close to The Old City/Market Square (downtown area with some excellent restaurants and other fun stuff).  

You will want to check out The Vol Navy rolling in Friday and early Saturday, and (if you don't mind the crowd), Calhoun's on the River is an excellent place to grab some great BBQ and watch the boats roll in.  The Women's Basketball Hall of Fame is on that end of town, as well...so if you are interested, it is very cool.

Just note that Knoxville/Knox County is very spread out.  If you are staying in West Knoxville, there will be plenty of restaurants and hotels...but it can take quite a while to get to campus from there once game day traffic has started up.  If you get there a few days early...you should check out Sullivan's (only a few miles from Campus).  The owner Charles Irvine went to UT, and his wife Monica and their son Sawyer are both BYU alumni.  

September will be hot and humid.  You are at the foothills of the Smokey Mountains, which will be much more pleasant leading up to the game...and there are plenty of lakes nearby to rent boats (personally, I recommend Norris Lake) if you are going to be there a few days early.  

The best tip...plenty of water, and clothing that breathes...It won't be much hotter in Knoxville than it is in Provo (right now, it's only 1 degree warmer here than it is there)...but it will be significantly more humid.  Looking at the weather history...the average high for September 7th in Knoxville is only 85 degrees and the average low is in the mid 70s but the humidity typically runs from 45 to 90% thorughout the day.  With a 7:00pm kickoff it should be much better than it would have, had we been the 3:30 game. 

As the game gets closer, I will post more detailed info on Gameday activities.