found this:
The point of capturing flags and killing enemies lies in the game's ticket structure. In the
upper right corner of your screen, on either side of the minimap, you'll notice two numbers. The
number in blue is the number of tickets remaining for your team, while the number in red is the
number of tickets remaining for your opponents. (Unlike in previous games, these colors aren't
assigned to a specific side; you can be MEC or USMC, and your tickets will always be blue.) The
ultimate goal of the game is to reduce your opponent's tickets to zero, with the most efficient
method of doing so to just kill them a lot while not dying. Each time you kill an opponent, you'll
reduce a ticket from his or her team's total. The key to capturing flags, though, is that in most
game types, you can cause the opposing team's tickets to automatically drain or "bleed" by
controlling more than half of the flags on the map. Doing so will not only cause a steady loss of
tickets, but will force your opponents to spawn in a fewer number of locations and will reduce the
number of vehicles available to them, making it harder for them to take over other flags. By the
same token, though, the more flags under your control, the more spread out you'll be, so you'll
need to watch the flags behind the front lines to ensure that no enemies parachute into an
undefended base and start capturing it.
go here its a pretty good guide:
http://www.bestgameplayers.com/bf2.pdf