Just educate first the people that you're talking to if they're interested to know more about bitcoin. Tell them the good things about bitcoin but don't forget to include the risks that someone will take if they ever decide to invest in bitcoin.
Obviously this is the best way to go about telling people about buying Bitcoin if you want any of friends to get involved , give them the education first in order for them to really understand what Bitcoin is and how it works, This was same way I got one of my friend interested to invest money into Bitcoin after has gotten the necessary info and proper knowledge about Bitcoin.
Avoid giving guarantees because that's where you're just making yourself in trouble because the person you're talking to might blame you later on if resuls didn't go according to what you've guaranteed.
Normally no guarantees when it comes to digital/cryptocurrency investment, everything is on trial method right now and you can only tell people about future expectation of Bitcoin base on historical data.