Check out SeatGeek.com to find a comparison of various sites for the best prices available.
A bit of information I learned from working within the ticket market... brokers have a csv file that they upload to various sites, such as Razor Gator, and Stubhub, Tickets Now and Ticket Network. The file will contain all ticket inventory and their pricing per ticket. Meaning, you will see a lot of the same inventory on secondary sites. Fees may vary, as will guarantees.
Ticket prices do drop the closer you get to game day, as sellers/brokers get nervous about not being able to sell their tickets AT ALL. You'll notice this in the last 24 hours before the tickets fall off each respective site. I think Stubhub will keep tickets up the longest, as does Ticket Network.
Usually a handful of sellers will start to drop their prices, causing the other sellers to try to undercut them to ensure their tickets sell. BUT if the sellers are sure they won't be left with unsold tickets, they'll likely keep their prices stagnant and the let the buyers pony up the cash. NFL games don't see prices drop - especially for the good team (not the Dolphins or Raiders of the world).
While working for a ticket agency, I had the NY Jets account - for which I was responsible for selling 500 upper level seats per game. Generally, I would stagger the ticket groups while staying out of the bottom 15% prices because I knew people were undervaluing their tickets and that the demand would eventually find its way to my tickets - allowing me to pull a profit.
But on Friday and Saturday, to ensure I sold off the remaining tickets, the staggering of prices would be less dramatic and I would move prices closer to the bottom of the market. This would ensure a sell out every time.
Baseball and basketball were different... with little demand, you sometimes has be create a new floor on the market to ensure the sell of tickets.
