Fallout New Vegas- How do I get Boone as my companion?

You might want to load a previous save, and re do the quest. If you dont have a high enough speech you need to wait for Jeannie May Crawford to leave the lobby thing at night then break into the safe she has behind her desk. There will be a note that proves she is guilty. Lead her in front of the dinosaur watch her die, then show the note to Boone.