If you don't have access to a CUAD parking pass, a lot of Clemson churches and businesses close to downtown offer game day parking. For example, First Baptist Church parks about 100 cars and is located at 397 College Avenue. From Hwy 123 (Tiger Blvd), turn onto College Avenue and the church is on the right just before first traffic light. The Catholic church and Lutheran church are in the same block. The Presbyterian church has parking but I think they only sell season passes...just like the city parking garage.
It's an easy walk to the stadium, plus you can enjoy the stores, restaurants and bars downtown.
Most of these downtown lots are first come, first serve, so you need to get there several hours before game time.