* If it's a withheld/private number, I don't answer.
* If it's a number I don't recognise, I don't answer.
* If it's a number I recognise from work/a client, I don't answer.
* If it's a number I recognise from a friend, I don't answer.
* If it's a number I recognise from a direct relative, I don't answer.
* If it's a number I recognise from a very direct relative and I've been called several times in the last minutes, I start pondering if I should pick it up or not. I usually do not, but ymmv