In order to get this achievement, you need to convince every companion in Fallout: New Vegas to accompany you. Companions from DLCs are not counted.
You will need to hire and travel with the following companions in one playthrough:
- Arcade Gannon: He can be found in the Old Mormon Fort in Freeside. In order to recruit him, you will need to have or do one of the following: High rep with the Followers, completed the "High Times" quest, Speech 75, the Confirmed Bachelor perk, or Intelligence of 3 or lower. If you have positive rep with Caesar's Legion, he will not join you under any circumstances.
- Craig Boone: He can be found in Novac on the top of the Dinky the T-Rex at night. You will need to complete "One for My Baby" to unlock him as a companion.
- ED-E: He can be found in the Nash Residence in Primm. To unlock him as a companion, you will need to repair him. This requires passing a Repair check of 65, a Science check of 55 and a Repair check of only 35, or by finding three scrap metals, two sensor modules, and scrap electronics.
- Lily Bowen: A mutant who can be found in Jacobstown. You must complete the quest "Guess Who I Saw Today" to unlock her.
- Raul Tejada: He can be found in Black Mountain. You will need to complete the quest "Crazy, Crazy, Crazy" to recruit him.
- Rex: The King's pet dog. You must complete "G.I. Blues" and "Nothin' but a Hound Dog" to unlock him as a "full" companion. Rex can be used as a companion without completing "Nothin' but a Hound Dog", but he will not give you any perks.
- Rose of Sharon Cassidy: She can be found in the NCR Barracks at the Mojave Outpost. To recruit her as a full companion, you must complete "Heartache by the Number". Depending on the outcome, she will give you two different perks in addition to her base perk.
- Veronica Santangelo: She can be found at the 188 Trading Post. To recruit her as a companion, you will need to complete the quest "I Could Make You Care". If you insult the Brotherhood of Steel while talking to her for the first time, you will not be able to recruit her.