The key to bribery (well, heck the key to keeping members of any "evil" organization's mouths shut), is to find something they are really really embarrassed about, some sexual fetish, something secret about their family. Or, promise to absolutely put them in prison over some crime they committed. For the later, ever better entrap them to commit the crime first and record it. All that coupled with a reward -- if they need money, offer money (maybe in the form of a consulting business in a NSA front company with this purpose in mind).
No, the key to bribery is that once someone accepts money, you have two hooks in them:
1., They are willing to sell you intel for money.
2., You can now blackmail them as they accepted a bribe.
Point 2 is the reason you should never accept bribes when doing business, especially abroad and everyone tells you "it's normal". they're just waiting for a foreigner to get exposed, take your passport and have fun with you. see Russia, etc.
Oh boy. Oh yes it is. You don't bribe someone for information unless you have dirt on them, otherwise there's nothing to stop them turning traitor on you. If you don't have dirt on them, you just invent some. Doesn't matter. People don't fact-check - if the media says it, it must be true.
The CIA typically recruit through a combination of carrot and stick - i.e. bribery and blackmail.
"Hey dude, let me tell you about this sweet slightly dodgy thing I can get you in on."
... ...
"Oh by the way, I hope you like all that money you made. I work for the CIA. Work with us or go to jail, your call."
More commonly than not it's not about self-preservation, rather protection of loved ones - read up on Operation Mockingbird, which was driven pretty much entirely on this basis - luring journalists in with a subtle bribe hook, then using it to blackmail them.
