The basic rules
There are a few basic rules that add depth to the game of Tol Barad. The most important part of these rules depend upon whether you're attacking or defending.
If you're attacking Tol Barad, you win as soon as you capture all three flags. When you die, you resurrect near the flag you were attacking. There are three locations with siege engines. You can park the siege engines by the towers to extend the timer, giving you longer to win the three flags. The attacker's challenge is all about coordinating your strike teams so that you get all the flags simultaneously.
If you're defending Tol Barad, you win by letting the timer run out. That means your challenge is one of endurance as well as coordination. The moment all three flags are owned by the attackers, the game is over. You can't risk letting the enemy's getting even two flags for longer than necessary, because the second that third flips, it's game over. If you die while on defense, you resurrect at the center of the map. This is a good situation because it allows you to quickly reallocate your team equally across all three flags.
If the attacker owns two flags, then the slider will move considerably faster on the third. Owning two flags is not a neutral situation because of how much faster the slider moves in that case.
Even though the rules for Tol Barad are a little different depending on whether you're attacking or defending, the general tactics are about the same. You want to deliver a slightly more powerful force to where your opponent is the weakest, forcing them out of that flag.
When attackers have two out of three flags, then obviously they must go to the third. The danger here, of course, is that if you leave the first two flags insufficiently defended, the defenders will easily take it back.
Tol Barad comes down to smash-face PvP. Warsong Gulch depends on your ability to run with flags. By contrast, in Tol Barad, if your force can't force the other team out of the flag areas, then you can't take back the base.
Be sure you always leave at least two or three people to defend your owned flags; this will allow them to yell for help before getting overwhelmed.
Since Tol Barad relies so much on personal performance, here are some tips to help make sure you can do well in the battle.
Duck and cover. There are lots of corners, poles, and obstacles in Tol Barad. If you have the option, get behind them. Don't give hunters and casters a chance to go hog wild on you.
Pair up. Grab a partner to watch your back, and in turn, watch his back. This is especially important because rogues will take the opportunity to stunlock and gank people who stray from the pack. If a pair is protecting one another, rogues will have less chance to do that.
Heal. Healing is a key part of winning in Tol Barad. Because of its fast-paced and energetic nature, a lot of the damage in Tol Barad is relatively "incidental." Damage dealers rarely get the chance to lock down on a single target and really unload. Throwing heals will minimize the likelihood of half-hearted opponents' easily killing your team.
Protect the healers. Healing is important; therefore, protecting the people who are doing that healing is equally important. It's also a great way to mow down the enemy; if opponents are trying to kill someone that's not you, you're left relatively open to fire through a full rotation of damage.
There are a few things that can significantly set back your team. Here are some things to avoid (or at least be really sure of the situation before you start doing them):
Don't fight away from the flag. The goal of the game is to flip the flag; the farther from the flag you are, the less likely it is that you'll take it. Fighting on the roads tends to be the ultimate sin, because it's a distraction.
Don't chase siege engines. If you don't pump out huge amounts of DPS, it probably won't be worth your time to chase down siege engines. It takes one attacker less than a minute to set up two siege engines on a single tower. However, if you're on defense and it seems like a chunk of attackers are actively defending siege engines ... make them defend it! If they're defending a siege engine, they're not attacking a flag.
Don't think you're safe. Tol Barad is fast-paced. You can't stop because you think you're safe. You've got to stay focused and keep pushing to win, or you'll lose ground as soon as you relax.
All this being said, Tol Barad is a lot of fun. It takes some time to really get the hang of it. Don't get frustrated if your faction seems to lose a lot, because everyone feels that way. Keep trying, keep practicing, and you'll get there.
Visit the WoW Rookie Guide for links to everything you need to get started as a new player, from how to control your character and camera angles when you're just starting out, to learning how to tank, getting up to speed for heroics and even how to win Tol Barad.