Come back to the Valley
With the release of Patch 2.4 many things have have changed in PvP in general and Alterac Valley specifically. From being able to join as a group, to Alliance captain buffs, to warmaster / general buffs for both sides. It is worth checking it out, as the changes seem to have leveled the playing field, so both sides have a more even chance at victory.
The most common way to victory in Alterac Valley is by killing the enemy Warmaster or General. While you can win by running the opponent out of reinforcements, killing the warmaster is far come common.These final NPC's are found in the enemy headquarters and are guarded by several marshals. All warmasters and marshals are buffed by each other for every one that remains. The buff is a stacking increase of health and damage by 25%. This makes it very important to capture each tower to ensure the corresponding marshal de-spawns, and removes a buff from the Warmaster.