For biwiring you would run two pairs of speaker wires for each speaker rather than the single pair per speaker normally used. At the receiver end, both "red/plus" wires would go to the "red" jack and both "black/minus" wires would go to the "black" jack. At the speaker end you would remove the jumpers between the two pairs of jacks, hook red/black from one pair to the mid/tweeter jacks and red/black from the other pair to the woofer jacks.
I don't think many people on this board feel it is worth the effort, but a few people swear by it.
Bi-amping is the same idea but you need two amplifiers driven with the same signal (ideally through an electronic crossover. At the speaker end the wiring would be the same as for bi-wiring, but at the receiver/amp end the two pairs would go to different amplifier outputs.
Bi-amping is felt to add some real value if you have a good electronic crossover but is only really seen in large professional sound systems. One of the most obvious benefits is the ability to drive the woofer amp into clipping without frying your tweeters, so you don't have to worry so much about cranking the volume a bit too high for the amp's capabilities.