Arrens has put together an introduction to battleground strategies with some great tips for those new to PvP:
The key to winning AB is defense of nodes. If you race from the gates once the match starts and cap Farm only to ride off into the sunset picking a fight with someone on the road to LM, do us both a favor, won’t you? Shoot yourself with a shadowbolt. Because I will hate you. Instead, if you cap a node, have the good common courtesy to defend it. Ask a friend to stick around with you so you can chat and D up together. If you see the opposing team coming towards you, call it out in /bg. And wait for them to come to you. Never, ever, ever leave your post. Fight on the flag.
Good advice!
Cynwise's Warcraft Manual 
While I royally suck at PvP, I take comfort in the fact that, at the very least, I follow the above advice.