Wild Card: Side Bets

Wild Card: Side Bets is a main quest in Fallout: New Vegas, given by Yes Man.

Detailed walkthrough
The factions you need to talk to are:
 * The Boomers at Nellis Air Force base
 * The Brotherhood of Steel at Hidden Valley
 * The Great Khans at Red Rock Canyon
 * The Omertas at Gomorrah casino
 * The White Glove Society at The Ultra-Luxe casino

Each of these factions can be met in any order, and all have a quest associated with them. Upon successfully completing the associated quest, you will have the option to tell Yes Man what you have done. Alternatively, you can simply tell Yes Man to ignore the faction, thereby skipping the need to deal with them. Even if you've told Yes Man to ignore a faction, you can go back once you've earned their assistance and change your opinion of them through dialogue.

Essentially this quest is just a guidepost quest that points you to the other factions, actually earning their aid or solving their problems requires you to complete a side-quest that usually gives you reputation (reputation with the Strip for the casinos, or with the Boomers, BoS, or Khans) and sometimes special benefits.

Brotherhood of Steel
Hidden Valley is a fenced in area that has an odd phenomena during the night, dust storms concealing its bunkers. A few underground bunkers are scattered around the area. The Brotherhood bunker is on the west side of Hidden Valley toward the north end, and will be indicated by a tree stump on it. Upon entering the correct bunker, you will be interrupted by two Brotherhood paladins. They will ask you to strip down to your underwear, wear an explosive collar, and to enter and meet their leader if you want to side with them. (This section of the quest will not occur if the player has Veronica Santangelo as a companion.)

Although the Brotherhood of Steel will not side with you and Yes Man, you have two solutions:
 * Destroy Hidden Valley. Hack the self-destruction terminal on second floor (very hard), or pickpocket 3 keycards (from Elder McNamara, Head Paladin Hardin and Head Scribe Taggart) so you can generate password for self-destruction. When you activate the self-destruction protocol, the whole base will go hostile. Hacking the turret control console (hard) in Paladin Ramos' room, and setting the turrets to attack the Brotherhood of Steel members might be helpful. (Hint: Dressing up in a Brotherhood disguise will make everyone ignore you after you activate self-destruction)
 * Convince the Brotherhood of Steel to support the NCR. Follow the NCR quest line until you reach For the Republic, Part 2. Colonel Moore will ask you to eradicate the Brotherhood, and you can negotiate with the Brotherhood Elder. Elder McNamara will, after some convincing, support the NCR to avoid conflict with them. This option will not be available if you helped Head Paladin Hardin to become Elder; he will not ally the Brotherhood with the NCR under any circumstances. You can report to Yes Man before or after telling Colonel Moore.

Boomers
To solve the Boomers' problems you must complete the quest Volare!, which will earn you their assistance in the Battle of Hoover Dam (by way of a pre-War heavy bomber) and the ability to come and go freely from Nellis. Thump-Thump, a unique grenade rifle, and ample 25mm grenade ammunition and all types of grenades can be found in the Ant Misbehavin' side quest at Nellis AFB. If you want to pick up the rebreather, you can acquire it from Jack and Loyal after getting Pearl to trust you.

Great Khans
The Great Khans can either be convinced to help you (by completing the quest Oh My Papa) or to leave the Mojave for more fruitful areas. Or, they can be exterminated completely. It is also possible to get the Khans to suicide bomb Hoover Dam during the final battle through a speech check (75) with Papa Khan after you've gotten him to break the alliance with Caesar's Legion.

If you don't talk to Papa Khan before killing him you will not be able to complete the quest part with Yes Man.

White Glove Society
By dealing with the White Glove Society's problems with cannibalism during the quest Beyond the Beef, you can tell Yes Man that you fixed their problem, solving their portion of the quest.

Sometimes when you are doing this portion of the quest, Marjorie will not appear outside the Members Only area. This can be solved in two ways, both console commands: by typing "prid 0010d4e7" and then "moveto player", or by using the "kill" command on any White Glove. Loot them, then use the console to resurrect him or her. If you loot them, you get the key to Members Only area and a disguise so the White Gloves you encounter won't attack you; Marjorie should be inside.

Omertas
At the Gomorrah you can pick up the quest How Little We Know. If you choose to aid Cachino in breaking up what the bosses have planned then you can inform Yes Man of this fact. If you help the bosses in their plan to attack the strip you can also tell Yes Man of this completing that portion of Wild Card: Side Bets. Caution this will lower your reputation with The Strip but can be fixed by leaving The Strip for 3 days.

Completion
Once all the factions have either been ignored or their side-quests done, the player must simply talk to Yes Man again to complete the quest.

This quest is probably the longest in the game, simply for the fact it has five components, each of which is a quest chain with between 2 and 7 parts.