Heres Watkins Glenns website
http://www.theglen.com/
You can purchase tickets there online, it also has a wealth of information on seating, parking , events being held during the race ( always a great concert Sat nite ) and even entrance and exit maps that really help you plan getting in and out.
Watkins Glenn is really cool race! The area from turn one all the way to the chicane on the back straight has some great veiwing of ALOT of on track action ( although it appears straight on the track map its actually downhill out of turn one then uphill into a set of essays then into the back straight ) Another good area is the last turn before the Start Finish line.
Wear comfortble shoes and wander around the track, its an Experiance!! Have Fun