Answer 1: its when you just right bump on your thread and people can see it quicker. But you can't Bump more than once in 24 hours.
Answer 2: To do a PM you click on the persons name. Then you click "Start Conversation".
Answer 3: You can PM them and let them know and ask for their preferred payment method. (Usually Paypal or Bank Deposit) After payment has cleared they will most the card.