I would read the sellers product info/instructions. If I were to say in the product description to pm me first, then do so. Lets say that I put "will not accept po boxes" your order will probably be canceled if you gave me a po box. Then pm me and we can talk about it. (that was just an example) Or if you send me 1 btc on top of the order because you expect it to be overnighted. I would cancel. It would have to be pretty extreme for me to cancel unless there was an un forseen problem. But, I would never cancel an order that has been sitting there for a couple days. So far, the only reasons I have had to cancel is because the buyer didn't follow my instructions. Just follow the instructions from the buyer and you shouldn't have any issues. I encourage buyers to ask me questions if they are unsure of anything.