I have Mobile Authenticator and Trade Confirmations enabled
Friend requests without a specific comment will be ignored

Steamrep [steamrep.com]
Steamgifts/Steamtrades Feedback [www.steamgifts.com]
Backpack.tf Feedback [backpack.tf]
Steamtrades profile [www.steamtrades.com]
My trade offer URL

your profile must be public.
change "profile status" and "inventory" to public and remove the checkmark from "Keep your Steam Gift inventory private"
your payment items (TF2/CS:GO keys, TF2 tickets etc.) must be tradeable.
If you bought it from the steam market you have to wait 7 days.
Steam Market links: TF2 key - Tour of Duty Ticket - CS:GO keys

you have mobile authenticator and trade confirmations enabled
How to set up a Steam Guard Mobile Authenticator
Steam Guard FAQ
Steam blog "Security and Trading: Update"
If you don't have a mobile phone, you can use Steam Desktop Authenticator [github.com]