Use your minimap!
This is a very fast game and knowing where to go is key. If you spend your time running around trying to find the action, you will be more or less useless most of the time.
The circle moves with the cart. While this seems obvious, it is easy to get caught up in combat and suddenly find yourself outside of the circle.
Your team scores points for every player who is inside one of your colored circles - so, it is more important to stay with the cart than to kill your opponent.
If you're the leader, it's probably worth shouting "STAY WITH THE CARTS" over and over again ... annoying, but worth doing.
There are two places where the tracks split and the cart can go in either direction. The direction is indicated by a lighted arrow that sits on a SWITCH mechanism.
By clicking (and holding) on the switch, you can change the direction of the cart. Since one track is longer than the other, doing this will either increase or decrease the time it takes the cart to arrive at the dump point. So, in general ... if it's your cart, make it take the shorter route ... and if it's owned by the enemy, make it go the longer way.
THREE CORNERED CONTROL
If you clearly have the superior team, you can speed up the game by controlling three spots on the map.
Control each switch and set the arrow to send the carts north. This seems longer, but once you have done this, one person guarding the north intersection (shown in the green arrow in the image to the right) and one or two people guarding each of the switches will guarantee that you score two carts all the time.
With this in hand, the rest of your team can focus on the middle cart, with some pulling out for defense if either of the switch guards calls incoming.
This is also the best way to farm kills, as it traps the entire enemy team in the middle where they are bunched together and easy to find.
Because the capture points are at the ends of the mine tunnels, the middle area of this battleground is of little use.
Unskilled players will tend to congregate in the middle and surround carts as they leave the terminal. Rather than engage in a huge melee, from which it may be difficult to pull out and follow the carts, your team may want to control the ends of the corridors and wait for the carts to arrive.
This strategy works because the points scored when a cart "caps" are much larger than the points received by guarding the cart the whole way in.
A good starting plan is to control the end of the middle mine shaft and the switch at the eastern (or "lava") shaft. The eastern shaft is the shortest, but since it can be switched to its northern track, the junction needs to be guarded. However, if you control the junction, you can keep the enemy out of the shaft entirely and only send one or two of your team down with the cart.
If you can gain control of the middle corridor at its top end, well and good ... but you don't need that. For example, you can put your whole team on the eastern switch to guarantee control, and then send a ninja group down the middle corridor (or over to the western corridor) in time to take control of and cap the cart.