The best groups I've had have employed the strategy of running base to base to base and capturing them as they go, rather than just capturing a base and defending it the whole game. The reasoning behind this is that you'll be 'one step ahead' of the rest. Aka, by the time the group you just conquered manages to group up and get ready to assault again, you will already have another base in your hands, and they will waste a full group charging at a mostly empty flag (since you already left). This requires a LOT of coordination, however, and relies heavily on dominating mid. Of course, winning at all almost always involves heavy involvement in the PvE aspect. If you know exactly when nodes will spawn, you can have your floater group abandon capturing and running to the middle to take over. There's no reason to stay in mid when nodes won't be spawning, so don't waste too much time there.

Here are some dos and don'ts for PvP.

DO have people watching for how many people are incoming/attacking and call it out in alliance so the floating group (usually group B) can send help.
DO prioritize people from the same group staying at a particular area so it is easier to receive buffs/heals, particularly AoE ones.
DO use marks to show who to kill first -- and, big surprise, it doesn't always have to be a healer.
DO make use of your limit break, whether it is to LB the group on the flag (AoE stun/bind works well when coupled with this) or LB the PvE node that is worth the most points.
DO NOT chase enemies away form the flags, or 'fight on roads'. This is baiting, and more than once I have seen enemies come up from the rear to capture a flag while the defending group is far ahead fighting.
DO NOT complain in alliance chat how bad your group is, unless you are prepared to offer a strategy.
DO NOT gloat about how great your premade group is in alliance chat, because that just makes you look arrogant. A victory is a victory for all those involved.

Btw, I am also Adder, but obviously anyone can see this advice and use it... and I hope they do. I've had losses that were downright embarrassing, and victories that were embarrassing for the other teams. There's a lot of variation regarding how well a team is doing. I notice the Maelstrom on Primal seems to dominate during latenight, and Adder seems to do well during the early evening. That's a very small sample size of experiences though, but you get my point.

As others have said... the biggest thing is COMMUNICATION. The groups that communicate super well will probably score more points.