Hi,
In general, it would be best to take a pic of the item you have for sale, with your screen name written on a piece of paper with todays date on it. (Assuming you have the item in hand)
Next, set your asking price, crypto payment of choice, make sure to include any special details if necessary.
Specify shipping costs, time frame, and who pays for what.
I would highly suggest to offer to use a trusted forum escrow, this will eliminate a lot of scam accusations on your part, and a buyer will feel safer using a trusted forum escrow for any deals.
I can personally recommend minerjones to act as escrow from many successful deals and trades done.
https://bitcointalk.org/index.php?action=profile;u=346731Update your OP with that info and you should be good to go.
Thanks!