How do I get a permit for a system to make a delivery?

I picked up a delivery at Gorbachev Station to be delivered to Sirius, but I can't jump there as I don't have a permit. How do I get one for Sirius? If I encounter another system that needs a permit, how do I get a permit for it?

I believe that when a system requires a permit, you need to build up reputation with the faction that controls the system in order to get a permit.

Look at the galaxy map to see what faction controls the system, find systems (or at least stations) they control that you can get to, look in the bulletin boards, and run some missions for them.

Update:

I believe this answer is correct for that system, however, for a number of Federation and Empire controlled systems, you need to build up rank instead of reputation with those major factions. You get rank by doing missions for Federation/Empire affiliated factions until you get a Federation/Empire Naval mission and then doing those missions.

Federation systems requiring Federal Navy rank: Sol, Beta Hydri, PLX 695, Ross 128, Exbeur, Vega, Hors (list probably not complete)

Empire system requiring Empire Navy rank: Achenar, Summerland, Facece (list probably not complete).

Note: in my experience, you get the permit in the form of a "go to system X to pick up another mission, and here's the permit" type mission, and if you go to that system, there's nothing special...

Also, there are some systems that are just plain locked down, with no way to get a permit. I believe these are there for some possible future additions to the game. I don't think any of those show up as having stations in them, though.