I met them for the first time in September. It was pretty easy, actually...
Me and my buddy got to the arena very early, and we saw Axe and Fredrik just hanging outside the tour bus. We simply went up and started chatting with them, and then Mike, Per and Martin came near them, and we talked to them as well. Got a pic too, which was nice (it's on the opeth fan site, Sept 19 in Worcester, MA).
Overall, they all seem very personable, and easy to talk to. The only one that seemed to be on the quieter side is Axe.
I recommend just getting to the show early, about the time when their bus arrives, and then just simply go and talk to them.