With the cars pitted in the infield, there's gonna be some blind spots no matter where you sit(mainly turns 2 and 3). Higher is of course better, so get there early to get a good spot. I sit in the top row of the covered grandstands which I think offers the best overall view of the track and speed thrill, plus little dust. The ends of the covered grandstand are open seating with the turn 1 end being the family section. The rest is reserved with the top rows being season reserved and the middle to lower $2 extra at the window. My brother loves sitting on the turn 1 hill which offers a unique view of the cars coming at you and going into turn 1. It's an awesome perspective but be sure to take goggles if you sit there. They also have two sets of open bleachers on the frontstretch where my parent like to sit and a cement terraced lawnchair section which is a nice place to sit but you have to pay $2 extra per spot.
Food, I like the chili, pizza, chicken and fish sandwiches and it's the only track where you can get fresh roasted peanuts. The food is reasonably priced, lower than most tracks I've been to.
You'll be sure to get a good speed buzz from Selinsgrove. It's a very fast track and you sit a little lower and closer than anywhere else.