One very big tip. Never, ever respond to someone who contacts you about selling you their points or their reservation. You need to be the one to make contact first. You can respond to posts on the Rent/Trade Board, but no where else. This is just one way unknowing guests have been swindled out of their money by con artists posing as DVC owners renting out points.
One other very big tip. Never purchase a reservation from someone who tells you there will be a fee of $XX due when you check into the DVC resort. That is a big clue that they are trying to sell an RCI trade which is not legal. Both DVC and RCI can cancel a reservation that has been sold and you would be out any money you paid for that reservation. Most of those reservations are Fri to Fri or Sat to Sat and most likely a SSR one bedroom villa.