1. Go to Novac between 9 PM and 9 AM. Find the giant dinosaur and enter it. Once inside, head up the stairs and go through the door at the top. You should meet a man named Boone. Talk to him about his wife and you will receive the quest to find out who sold his wife off to slavers so he may kill them. He also gives you his beret to wear as a signal to fire on the person you bring in front of the Dino.
2. You are then given the task to talk to select inhabitants of Novac. Luckily, you only need to talk to one of them in order to progress in the quest. This person is No-bark Noonan. an older man that seems a little out of his mind. You can find his shack behind the motel. Talk to No-Bark about Boone's wife and he will tell you about strange business in the motel lobby. If you have a high enough Speech level you can finish the quest without evidence. Just talk to Boone after talking to No-bark Noonan.
3. Head to the Dino Dee-lite front desk and check behind the counter to find a safe in the floor. This safe is locked and will require you to either pick it (Easy skill) or pickpocket the key from Jeannie (there is no loss of Karma). Inside the safe you will find a note titled bill of sale. This document tells of how Jeannie May Crawford sold Boone's wife off to Legion slavers.
4. Now that the evidence has been obtained, wait until Boone is at the sniping spot (between 10 PM
and 9 AM) to confront Jeannie and ask her to take a stroll with you in front of the dinosaur. Once in front of the dinosaur, put on the beret and Boone will kill Jeannie (remember that Boone has to be in the T-Rex before the dialogue choice that allows you to lure Jeannie May to get shot appears).
5. Head up to Boone. He will ask you how you knew it was her and you can tell him about the bill of sale you found. If you did not get the evidence, it is possible to pass a Speech check (55 Speech required). If that fails he may try to kill you or get angry, snatch his beret back, and say that he doesn't ever want to see you again, eliminating the option of him being a companion. If you told him about the evidence, you can keep talking to him and convince him to become your companion.