[Ken Leung]

A few general ways you can grab the goals.

First, if you are doing one goal, you would probably grab the goal in front when your robot rush toward the goals. Or you can do it on your side, although you will need to compensate for that one goal dragging one side of your drive train.

Second, if you want to grab two goals, you can either do one on each side, or one front one back, or have a telescoping/very long arm extend past the first goal to grab a second goal.
Grabbing two goals probably need some sort of arms on your side extending out to reach for both goal at once to do it fast, or else you you will have to aim to grab the second goal from some other robot.

Grabbing three goals... you can either extend three long arms out toward all three goals, or you will have a really tough time trying to get a goal or two from opponents... If you are lucky enough to get all three goals, then you can hold them around your robot, and basically push forward with a strong drive train, because the opponents will forget everything else and try to stop you.

So that's some of the general position you want your robot grabbing the goals. As for the actual mechanism, you want to design something that will easily slide in between the poles, and lock on really fast. Design some sort of gate latch so that the physics of you mechanism likes to hold onto the pole(s). They can be grippers, hooks... etc. Just try to avoid having to use power to keep the goal(s) in your procession.

You also want to design that mechanism so your driver don't have to point your robot too accurately to get the pole(s)

You can just grab one pole per goal, or you can grab two pole for a solid connection between your robot and the goal, so when your robot is moving around, the goal will always stay the same relative to your robot.

Also, depends if you want more traction or not, you can lift up the goals slightly to add more weight onto your robot.