As mentioned above check out Latimore Valley home of the Eastern Museum of Motor Racing.
http://www.emmr.org/
Access to the infield is via a tunnel down at turn one. You will not want to miss a chance to watch some of warmup's or a heat race from there. Also consider watching some from beer hill there is a small set of stands outside turn three and you can watch the cars come straight down the back straight. Lots of good seating and the lighting there is very good. As for Lincoln get there early as they have less seating and they typically get a very good crowd. There is also a tunnel for infield access at turn 4 and you can take in some race action in the turn 3 and 4 area. Lincoln also has some great food choices. Check out the BBQ trailer and seafood down toward the turn 4 area behind the stands.