The player requires 5 "history" points with Boone. These must be earned with Boone in your party, listed below:
"Camp McCarran
When torturing the captured Legion POW Silus at Camp McCarran,
if he dies during the torture: +1."
Already did that without Boone in the party
"During the mission 'I Put a Spell on You' at Camp McCarran
If you confront and kill the spy in act (Capt. Ronald Curtis): +1.
If you disarm the monorail bomb: +1."
Already did that without Boone in the party.
"The Fort
Killing Caesar at The Fort: +2."
Just did that with Boone, but 2 trust point isn't enough.
"Legion Raid Camp
During the side quest Booted at Legion Raid Camp, rescuing the hostage Powder Gangers: +2"
Already did that without Boone in the party.
"Nelson
During the side quest Back in Your Own Backyard in Nelson
If you kill the hostages: +1.
If you save them: +2."
Already did that without Boone in the party.
"Camp Searchlight / Cottonwood Cove
During the side quest Eye for an Eye (begun at Camp Searchlight; executed at Cottonwood Cove), eradicate the Legion for: +2.
After killing Aurelius of Phoenix in Cottonwood Cove."
Already did both of those without Boone in the party.
"The Tops (or The Fort if Benny escapes)
Confronting Benny at the beginning of Ring-a-Ding-Ding.
After the mission 'Ring-a-Ding-Ding' if you kill 'Benny'."
Already did that without Boone in the party.
"Killing Vulpes Inculta: +1
Also, during Wild Card: Change in Management, if you kill all the legionaries including Caesar, it should bring up the dialogue option after Boone mentions Caesar's death."
Haven't done that yet but I don't even know where Vulpes could be.