Not to mention: Jumpseat Ettiquette...
I tried jumpseating on a few different carriers a week or so ago on a trip to IAH and back taken for personal reasons. It was.. enlightening.
First off- read the article on ettiquette on jumpseating on AirlinePilotCentral. I tried it and was more or less unawares and probably made an ass out of myself. I know better now. There's unofficial protocol to be followed, unless you want to make a name for yourself as being 'that guy'.
Non-rev travel aside, if you want to jumpseat, ask the gate agent if you can ask the captain for a ride. Once the agent verifies you clear in the system, venture on down when it's convenient for them and the crew. Ask the lead flight attendant if you can ask the captain for a ride. This, of course, assumes there is at a minimum an open cockpit jumpseat that the airline in question will let you occupy by policy.
Then, politely introduce yourself to the captain and f.o. and present your credentials (airline ID, passport, forms, etc..) and ask for a ride.
It's still the captain's discretion. If there are seats available in the back, he might ask you to be there. Otherwise you'll wind up in the cockpit jumpseat. If you do, do your best impersonation of a flight engineer and watch everything. Don't attempt to assist or involve yourself unless asked to do so by the captain.
If, as happened to me the other day- they overseat the flight and you suddenly find yourself the odd man out- politely thank all involved for trying and try to get on something else. Everyone involved doesn't owe you anything and just went out of their way to help you out. They'll remember how you act.
This stuff pays off in spades with your colleagues in the regionals, and is a definite must with your more seasoned counterparts at a major. They notice. It's up to all of us to maintain and uphold the dignity of our profession and not be 'that guy'.
Hope this helps.