1. Don't pay for shipping
2. Don't buy a new pin
3. Don't buy something you can't inspect in person
4. Use this price guide! http://www.bostonpinball.biz/ebay_0515_4.htm
5. Don't pay more than $200 over the "Average Since 11/25/14"
6. Offer LESS than the average if the game isn't nice.
Don't ignore older Sterns, because there are some great deals to be had. I sold my NASCAR for $1800 and it's a very fun, dependable pin. Most Sterns under $3k have already fallen as far as they're going to.