Simply complete all missions given from NPCs/Bounty-Board within the second area. Clap-trap quests also count towards this achievement. Here is a list of every mission in the Rust Commons:
*** Spoiler - click to reveal ***1.Scooter's Used Car Parts
2.Claptrap Rescue: New Haven
3.Claptrap Rescue: Tetanus Warren
4.Corrosive Crystal Harvest
5.King Tossing
6.Is T.K. O.K.?
7. Hidden Journal: Rust Commons West
8. Scavenger: Submachine Gun
9. Firepower: All Sales Are Final
10. Firepower: Market Correction
11. Firepower: Plight Of The Middleman
12. Jack's Other Eye
13. Like A Moth To Flame
14. Two Wrongs Make A Right
15. Middle Of Nowhere No More: Investigate
16. Middle Of Nowhere No More: Fuses? Really?
17. Middle Of Nowhere No More: Small Favor
18. Middle Of Nowhere No More: Scoot On Back
19. Power To The People
20. Another Piece Of The Puzzle
21. Not Without My Claptrap
22. Up To Our Ears
23. Claptrap Rescue: Krom's Canyon
24. Earl Needs Food Badly
25. Missing Persons
26. Scavenger: Shotgun
27. Altar Ego: Burning Heresy
28. Today's Lesson: High Explosives
29. Hair Of The Dog
30. Hidden Journal: Rust Commons East
31. The Next Piece
32. Altar Ego: The New Religion
33. Altar Ego: Godless Monsters
34. A Bug Problem
35. Relight The Beacons
36. Green Thumb
37. Jaynistown: Unintended Consequences
38. Jaynistown: Cleaning Up Your Mess
39. Bait And Switch
40. Claptrap Rescue: Trash Coast
41. Claptrap Rescue: Old Haven
42. Bandit Treasure: Three Corpses. Three Keys.
43. Bandit Treasure: X Marks The Spot
44. Jaynistown: Spread The Word
45. Jaynistown: Getting What's Coming To You
46. Circle Of Slaughter: Meat And Greet
47. Circle Of Slaughter: Round 1
48. Circle Of Slaughter: Round 2
49. Circle Of Slaughter: Final Round
50. Seek Out Tannis
51. Meet "Crazy" Earl
52. Claptrap Rescue: Scrapyard
53. Get Off My Lawn!
54. I've Got A Sinking Feeling
55. Wanted: Fresh Fish
56. Earl's Best Friend
57. House Hunting
58. Smoke Signals: Investigate Old Haven
59. Smoke Signals: Shut Them Down