Bounty Hunter Missions are an Extra Bonus mission styled stages where you play as the Bounty Hunters, on a mission to collect various characters for Jabba the Hutt. These take place in existing levels and require that you head through and find the character you're looking for.
These are found in the door with Jabba's head on it between Episodes IV and V in the Cantina. Unfortunately, they are locked from the beginning of the game, and you have to complete the Story completely before being allowed access. To unlock the Bounty Hunter Missions, all 6 Bounty Hunters must be purchased from the Cantina, those being Boba Fett, Dengar, Bossk, Greedo, 4-LOM and IG-88. Once these six are unlocked, the Bounty Hunter Missions are available.
You aren't allowed to use Extras in this mode. Which means no invincibility. As such, I suggest using Boba Fett at all times, as he has a powerful gun and can hover around as well. Astromech and Protocol Panels are not a problem, as 4-LOM and IG-88 can use both just fine.
You'll notice a character portrait on the bottom of the screen, simply put, the more clear it gets, the further away from the character you area. It's only a very basic guide however, and admittedly, not very good.
Note: I will be putting the first two paragraphs of the crawl here, as they are the same for every mission. The third paragraph changes:
The vile gangster Jabba the Hutt plans to kidnap leading figures in the Rebel Alliance, threatening to hand them over to Imperial forces unless a ransom is paid.
Naturally, the evil Hutt intends to take the ransom money, trade his prisoners to the Imperials regardless, and pocket a double bounty.
Walkthroughs are below: