Steam offers if you want a response.

You suggest a trade and:
If it's me downgrading you are overpaying.
If it's you downgrading I am overpaying.
Multiple items for one, means the party with multiple items overpays.
Flip-, gut-, falchion-, hunt-, butterfly knife, Skins, Stattrak or BattleScarred = you overpay
Applied stickers mean jackshit.

Leave a note in the trade if you want me to look thru your inventory and suggest some adds from there.

You will get blocked for the following reasons:

Adding me without my consent.
Offering real money, giftcards etc.
Thinking this is a quicksell and offering me 30keys like I'm a crackwhore in detroit looking for a fix.

TL:DR the usual trading jibber jabber.