1) Never trust anyone who says Invest your bitcoins here/there and we will show how they grow down the line ! Never trust anyone and transfer your bitcoins into any wallet,once they are gone they are gone forever ! So please !
this is the obvious scam but the less obvious one that is common nowadays is the cases where they tell you they can help you "make profit" is an investment in some shitcoin they want to pump, in other words they don't take your bitcoins directly to their wallet, they instead take it from you indirectly by encouraging you to buy their sell orders of the shitcoin they want to dump!
they disguise it in form of "investment groups", or "signal channels", and things like that.