You pretty much destroy the right pillar at the entrance to the bank when you are facing the bank still in a helicopter. Try to do it as quickly as possible until the next police cars arrive. And the civilians you just press use button on them and they will run away. I didn't do any of the secondary objectives until I found out in some video.

Thanks. I know how do to them, I'm just wondering what are the effects of missing them (like letting civilians die).

As far as I know there are none, it's just some padding to entice you to try and extract the maximum out of the game.
Or I haven't been paying attention and some missions require you to complete secondary objnectives as well to activate the exit trigger, but I don't think so.
I see it mainly as fluff to add things to do.

Thank you. It seems to be just fluff indeed.