After completing or canceling the tutorial quests given by Sunny Smiles, she will suggest that you visit the saloon in Goodsprings.
Enter the Prospector Saloon, where you will find Trudy arguing with Joe Cobb about the whereabouts of Ringo, a trader who is hiding out in the town. Once Cobb leaves, the Courier can question Trudy about the argument and get more information about the Powder Gangers. The Courier should now have access to the previously locked gas station on the edge of town where Ringo is waiting.
You can also start this quest by talking to Doc Mitchell, who will mention that there is trouble in town.
Head up to the gas station, to the right of Mitchell's house. Ringo will challenge you when you enter, but talking to him will give the option to offer your help dealing with Joe Cobb. He will request that you attempt to enlist more help from the townsfolk. The Courier can do this by simply asking Sunny Smiles, who will instantly pledge to join you in the fight. She provides you with optional objectives to rally more support.
Completing the optional objectives will require convincing the Goodsprings inhabitants in question, through skill checks in dialog. If the player lacks the necessary skills to pass skill checks, there are many skill magazines that can help scattered around town.
Skill magazines can be found randomly in mailboxes around Goodsprings and elsewhere, such as nearby Primm. Many merchants sell them on a random basis as well.
Convincing Chet to help out requires passing a Barter check of 25, or paying 1000 caps. He'll give the Courier a leather armor in ~50% condition, and promises to offer his stock to the town as well (equipping the generic Goodsprings settlers in sets of leather armor).
A Stealth Boy (+100 Sneak) can be used to pass the Sneak check with Trudy. One can usually be found in the Goodsprings schoolhouse inside the locked safe (Lockpick check of 25 required).
Doc Mitchell will give the Courier 3 stimpaks when asked for help. Passing a Medicine check of 30 nets 2 doctor's bags in addition.
A copy of Today's Physician, which boosts the Medicine skill by 10 (or 20 with Comprehension), can be found inside Mitchell's house, on a desk with a typewriter where the game begins.
You can also enlist Victor to join your side in the fight, but he fails to show up. Asking him about this later (before he leaves to Novac), you will find that he was shut down by an unknown person to keep him from fighting (Science check of 25 required).
A Programmer's Digest, which boosts the Science skill by 10 (or 20 with Comprehension), can be located in Goodsprings schoolhouse near the computer terminal, and there is a second copy on the shelf beside the overturned desks.
Even if the Courier doesn't recruit Easy Pete or Trudy, they will still probably help out in the fight. As will Chet, even though the Courier doesn't have the option to recruit him. Make sure Sunny Smiles doesn't die during the fight, as it will make it impossible to carry on the quest - see the Bugs section below for more information.
Once the Courier has enlisted all the assistance you wish to, return to Ringo in the gas station and speak to him to start the fight. Sunny Smiles will show up once the Courier commit to being ready. Follow Sunny and Ringo to the scene of the gun fight. Joe Cobb and the other Powder Gangers will approach the Prospector Saloon from the main road. Once all the Powder Gangers are dead, the quest is complete. It is, however, possible for any (or all) of the Goodsprings residents to die in the fight.
You cannot start this quest if you have already started Run Goodsprings Run. Ringo will decline your offer to help and claim he saw you being overly friendly to Cobb, after which the quest will be marked as failed. Even if you kill Joe Cobb, Ringo will still refuse your help.
Ringo will not accept your offer to help him if you have earned a negative reputation in Goodsprings, saying that he needs someone who is liked in the town, thus rendering the quest impossible to complete.
When asking around for supplies and help from Trudy and the other residents, it is possible to recruit Victor to help battle the Powder Gangers. You can usually find him wandering around Goodsprings or outside his shack near the Goodsprings schoolhouse. He will not participate, however, and when asked later will apologise and state that he must have dozed off. A Science check of 25 reveals that Victor was deliberately shut down using "Override command 16-Delta". He claims he has never heard of this command before.
Since he belongs to the NCR faction, approaching Ringo wearing armor of a faction that is enemies with the NCR will cause him to become hostile. If he turns hostile, you will fail the quest.
If the player does not personally kill any Powder Gangers during the fight or performs only stealth kills, the player will only earn a shunned reputation with the Powder Gangers, which isn't low enough to cause any Powder Ganger locations to be hostile to the player should they choose to visit.
Alternatively, one could complete I Fought the Law first, then return to Goodsprings to complete this quest.
Using a weapon that inflicts Fatigue damage to knock out Powder Gangers is a way to help Goodsprings win the fight without earning a Vilified reputation with the Powder Gangers.
If you steal the single shotgun from a house in Goodsprings before you enter the gunfight, Trudy will not have her gun in the fight.
You can kill Joe Cobb prior to the gunfight. Sunny Smiles will not mention him as being with the Powder Gangers when they attack Goodsprings, and there may be only five Powder Gangers although Sunny Smiles counts their number to be six.
When attacking Joe Cobb he may run into Easy Pete's house to hide.
The roof of The Prospector Saloon can be reached using the wooden barrels and crates nearby and offers a good vantage point during the fight.
pcps3xbox360 Sunny may die before the Courier talks to her, thus rendering the quest impossible to finish. [verified]
pcps3xbox360 When returning to the gas station after talking to the townspeople, the door may be locked, requiring a key to open. However, this key does not appear to be obtainable until the mission is over. [verified]
ps3 Upon entering the gas station to report to Ringo, the Courier may find the door unable to be interacted with thus trapping the player in the gas station. [verified]
pcps3xbox360 It is possible that the quest may not show up as active in the Pip-Boy, and it will be impossible to progress in it (the non-player character dialog will not show up). [verified]
pc After completing the quest, the inhabitants of the town who assist in the quest disappear. Using the player.moveto console command finds them in the Goodsprings home nearest the schoolhouse. [verified]
pcps3xbox360 When doing the optional quest to recruit the help of the Goodsprings Locals, Easy Pete may be at Black Mountain for no apparent reason. [verified]
pc When the Courier kills all the Powder Gangers, the quest does not complete, making the quest impossible to finish. This can be fixed by re-killing one of the Powder Gangers: [verified]
You can spawn a new Powder Ganger with the console command "player.placeleveledactoratme 00104c6a 1", which creates a new Powder Ganger at the Courier's location. However, this may cause savegame bloating.
You can also resurrect an already-killed Powder Ganger: Click the corpse of one of the Powder Gangers that showed up for the Ghost Town Gunfight. It is correctly selected if the top of the screen shows the target's name and refID. Use the console command "resurrect".
Kill the Powder Ganger again.
xbox360 When the Courier goes to tell Ringo that you're ready to fight, Sunny Smiles will come in and say something along the lines of "I'll be watching the Powder Gangers for when the time comes." Ringo will not go outside but stay in the gas station, and the only way to fix it is to restart. [verified]
xbox360 The corpses of Joe Cobb and his Powder Ganger band never disappear from the game. [verified]
xbox360 At random times after completing the quest you may be given it again, everyone will respawn and XP is granted after beating the quest again. [verified]