first of all, Hi guys

Am new member in here, i created an account to be able to sell a key for tf2 (manco suply crate key), yeah i know thats not to much, but am just trying to get some cash that's all, so what i am asking for is how i can sell it in here, and to avoid getting scammed, what should i do and what i shoud not do, that's all, and thank you!!