One rule I go by is never answer private numbers or numbers I don't know.

I have a leave message service so if it's important then they'll leave a message.

I've also noticed over time the scam calls seem to only ring 3 times and then hang up so once the call ends I go straight to block this number and block it.

Mind you I have 100s of blocked numbers on my phone, some may of been important but I'll never know.