Any tips for new guys?

use enchanted steam addon for your browser ;)

Helps a lot! Many people wouldnt have gotten scammed if the had used it ;)

Well in case of trading there is few rules that propably will save you but most importantly remember about common sense if deal is too good to be true its most likly scam also i reccomend to check if accounts are legit by using sites like steamrep. Also when trading keys with someone better dont go first if person you trade with isnt somone that you knew before or someone without lots of ammount of rep. other than that like i said lots of common sense and hopefully its gonna be alright so goodluck with that :)

Reddit has a handy guide. It's long but a worthwhile read.

If it seems too good to be real, its probably a scam, dont click on suspicious urls and never download anything from random people's links... Also use some extension like enhanced steam that helps you to check if someone is an impersonator

Always make sure a person is who he claims he is. On Steamgifts there is a button to go to a persons profile. If it takes you to a different profile then the one that claims he is that person, you're dealing with an impersonator. Also: use steamrep to check if users are trustworthy. Don't use +rep comments on steam profiles as an indicator. They can easily be faked and -rep can be deleted. Always use sites like steamrep (as said before) and steamgifts rep system.