My wife and I did the F1 race at COTA last year. We flew Southwest airlines and used their site to also grab a hotel in North Austin and a rental car. Flew out Friday afternoon and it was rainy and mostly IFR into the next day, so I'm glad we did the commercial flight.
We grabbed some $5 folding chairs from Wal-Mart and had the Gen. Admission wristbands, which were something like $100 each.
We drove to downtown and parked in a parking garage for $10 a day, then walked a couple of blocks to the shuttle busses (another $20 per person per day!). Parking at the track was just as expensive, if not more. We walked around on Saturday and saw most of the attractions in the main gate area, then crossed over the infield towards turn 1 for the qualifying. The hillside there was completely muddy, but we had a good view of the front straight and down towards the pit lane.
On Sunday for the race, the crowds were WAY larger for the shuttle busses, and when we got to the main entrance the line for security was very long. We hopped on the loop shuttle and rode that around to the other side of the track where turn 1 was, and the entrance there was not busy at all and we were able to just walk right in and find a good spot on the hillside. We could follow most of the race action with the big screen TV's across from the grandstands.
After the race, we went down towards the main grandstand and they opened up the gates and allowed everyone on to the track. We got to the podium a bit late for champagne.
Overall a very fun weekend. We didn't stay for the concerts. Austin has plenty of other places to see great live music.