Don't forget to carry your medical and certificate, have it ready for the captain to see if he so wishes and always ask for permission and thank them for the ride (even if you have a seat in the back). And once you hit the line, remember to return the favor. I jumpseat all the time (I don't commute) and it's the best benefit of this job! So don't abuse it, did I mention thank the crew (include the FA), they can make the experience an enjoyable one if they know you are crew and you are nice. Free TV, meals, exit row and first class to name a few.