Our own Zach Yonzon is putting together some great guides to the battlegrounds (WSG is the last one, and Arathi Basin is being worked on as we speak), but just in case that's not enough for you, Digo of Hyjal has written up a great (and succinct) guide to how the premades win battlegrounds. From WSG to AB to EotS to AV, he's got a terrific writeup of what needs to be done and how to do it to walk away from the BG with more marks than the other team.
He markets the guide as one for casuals, but it's got great tips for everybody: fight on the flags, not on the road. Make sure you've got something held before moving on. Send a druid after the flag and control WSG's midfield. Stick together and assist and heal. This is all stuff every single person who queues up for a BG should know (and unfortunately, it's also the same stuff that's yelled in every /bg channel because lots of players don't listen).
Great post, and a must read for anyone routinely going into the battlegrounds. If you aren't doing this stuff already, take the lesson, and do it from now on.