Don't buy from the professional scalpers. Try to find a family or a friendly couple that just needs to unload some at face value. That shouldn't be too hard to find, unless the Yanks are in town.

Print off a seating chart from the internet and carry it in your pocket so you know exactly where the seats are that your purchasing. If the seat has an obstructed view it should say so on the ticket so inspect it carefully before you buy it. If the seller is acting funny about you asking too many questions or inspecting the tickets then just walk away. There should be plenty to chose from.

I only go to games on scalped tickets because it's the cheapest way to get in. Look for a well dressed rich guy that has tickets to unload and doesn't want much for them. Seriously, it works. Good luck!