You are to be required to do the following..
1. List clearly the items you wish you to sell.
2. Include important details such as which system it is for (if its a game), as well as the price, your contact no.
3. Should you wish for the thread to be locked and preferred to be queried via PM instead, say it and we will assist you in locking the thread.
4. Update your thread before it reaches 4 weeks without an update, even if there's no development. Failure to do so will result in thread deletion. This is in order to reduce congestion and to rid the confusion whether the said item is still available for sale or not.
5. If the item is sold, update it as well.
6. This is a MUST. The buyer and seller are required to give feedback on the thread itself.
7. If the buyer is not a member, then only the buyer is required to do the above. Rate if you wish to.
8. Last and most importantly, Honesty. Don't be bullshitting in here. You've been warned. You'll risk getting permabanned for that offense.
An example.
Call of Duty 4 For Sale (PS3)
Good Condition, well taken care of and hardly played.
Will sell it for $60.
Contact me at this number : XX-XXXXXX.
Seller Feedback : Thanks to the buyer, was well on time for the trade.
Buyer Feedback : The item is indeed in top notch condition, no hassle with the buyer, great buy.
Please update your Buy/Sell/Trade topic before the 15th of April. Should there be no update, the moderators will consider those threads to be outdated and will thus cast it off the to graveyard section.

