Who are all of the companions and how do I get them?

Here's a pretty handy guide for all of the 13 companions you can receive.

You can "recruit":

• Codsworth (Robot)
  • Location: Sanctuary
  • Associated Quest: None
  • Romance: No
  • Perk: Robot Sympathy
• Dogmeat (Doge)
  • Location: Red Rocket Truck Stop
  • Associated Quest: None
  • Romance: No
  • Perk: None
• Paladin Danse (Human)
  • Location: Cambridge Police Station
  • Associated Quest: Call to Arms
  • Romance: Yes
  • Perk: Know Your Enemy
• Piper (Human)
  • Location: Diamond City
  • Associated Quest: Location Quest: Story of the Century
  • Romance: Yes
  • Perk: Gift of Gab
• Preston Garvey (Human)
  • Location: Museum of Freedom
  • Associated Quest: None
  • Romance: Yes
  • Perk: United We Stand
• Nick Valentine (Synth)
  • Location: Vault 114 (Park Street Station)
  • Associated Quest: Side Quest: Long Time Coming
  • Romance: No
  • Perk: Close to Metal
• Cait (Human)
  • Location: Combat Zone
  • Associated Quest: Side Quest (Companion): Benign Intervention
  • Romance: Yes
  • Perk: Trigger Rush
• Curie (Robot)
  • Location: Vault 81
  • Associated Quest: Side Quest (Companion): Emergent Behavior
  • Romance: Yes
  • Perk: Combat Medic
• X6-88 (Synth)
  • Location: The Institute
  • Associated Quest: None
  • Romance: No
  • Perk: Shield Harmonics
• Strong (Mutant)
  • Location: Trinity Tower
  • Associated Quest: None
  • Romance: No
  • Perk: Berserk
• Deacon (Human)
  • Location: Old North Church
  • Associated Quest: None
  • Romance: No
  • Perk: Cloak & Dagger
• John Hancock (Ghoul)
  • Location: Goodneighbor
  • Associated Quest: Miscellaneous: Recruiting Hancock
  • Romance: Yes
  • Perk: Isodoped
• MacCready (Human)
  • Location: The Third Rail (Goodneighbor)
  • Associated Quest: Side Quest (Companion): Long Road Ahead
  • Romance: Yes
  • Perk: Killshot