Here’s the Caesar’s Quest guide from wikicheats.
This is the main quest line that allies you with Caesar’s Legion. If you follow it to the end of the game, it will result in the Legion taking over New Vegas and the wasteland.
Be aware that Boone, one of your possible companions, hates the Legion and will attack them on sight. If you’re going to ally yourself with the Legion, you won’t want him in your group for any of the Legion quests.
Render Unto Caesar
You will get this quest once you confront Benny in the Ring-A-Ding-Ding quest. As you are leaving the Tops Casino, you will be confronted by one of Caesar’s men who gives you the quest. If you have a negative reputation with the Legion it will be reset to neutral so you can start the quest.
By doing this quest you will complete as many as three quests at once. Yes Man gives you the quest “Wild Card: You and What Army?” and Mr. House gives you “House Always Wins, Part II” and Caesar gives you “Render Unto Caesar.” All you have to do in order to complete all of them at the same time is make sure you have started them.
Before you leave on this quest, know that you will encounter some irradiated areas. Bring some Rad-X and some Rad-away.
Speak to the legionnaire on the dock of Cottonwood docks. He will put you on a boat to “The Fort.” When you get there, you will have to give up your weapons. Note: inside the fort is a trader named Dale Barton. He can repair items for you, but don’t do it. Because you don’t have your weapons on you, the game often freezes if you open his repair menu.
Go to the top of the hill and enter the tent. If you didn’t kill Benny, he will be there as a captive. Either way, Caesar will ask you to go to a bunker and destroy whatever is inside.
Leave Caesar’s tent and go around behind it. There is a group of tents down the hill, and behind them a building. Enter and you will get your weapons back. You will also get the Platinum Chip, if you didn’t kill Benny.
Enter the bunker and you will be able to speak to Mr. House. He will ask you to use the bunker to upgrade his robots. You can respond however you like, but you can always change your mind later.
Just past Mr. House is a security bot at the bottom of the stairs. Take it out. Behind the door next to it is a plasma rifle. Also in this room are some terminals you can hack if you have a science skill of 75 or more. In the next large room are two security bots, and a turret at the end of the hall.
There is another turret behind the next door. Then next room is a generator room. It his three security bots. The door on the far side of the room has a turret behind it. Up the stairs is a room with three security bots. This room also has a control device. You must either use the control device or destroy the bunker by overloading the generators.
Now you have to make the choice. As you can tell by now, there’s a war brewing between the NCR, the Legion, and Mr. House. If you want to ally with Caesar’s Legion and want them to win, overload the generators (which will destroy the bot army in the bunker). If you want to ally with the Mr. House or want to look out for yourself (the Wildcard quest line), then use the control device to upgrade the robots. If you don’t know what to do, the safe bet is to upgrade the robots using the control device.
Upgrading will complete all three quests. If you choose to destroy the robots you will complete only the “Render Unto Caesar” quest.
No matter which you do, once you do it, get out of the bunker quickly. Head for the door you came in. Several security bots will attack as you on your way out. If you don’t feel like fighting, you can just run out the exit. Once outside, go back to Caesar. He will reward you for destroying the bunker, even if you just upgraded the robots for Mr. House.
If you didn’t kill Benny earlier, you can speak to him now. Make sure he mentions Yes Man (his old partner). You can now kill him. You can also fight him in the arena, and if you win you will get his unique pistol “Maria.” Or you can free him. You’ll have to fight your way out.
Assuming you and Benny don’t attack the Legion, Caesar will then give you the second part of the “Render Unto Caesar” quest. He wants you to kill Mr. House.
Render Unto Caesar, Part II
Killing Mr. House is easier than it sounds. If you have the Platinum Chip you are able to walk right into Mr. House’s penthouse. When you are standing in front of House, look to the left, under the stairs. There is a terminal you can use. Make sure you really want to get rid of Mr. House, because when you use it, the robots in the room attack. You could try to fight them, but a better idea is to run into the room that opens. Inside you will see an elevator on your left, and next to it a terminal. Use the terminal to unlock the elevator, then use the elevator to go to the control room.
Once here, walk up to the terminal and unseal the chamber. You can then talk to Mr. House, if you like. Return to the terminal and either sterilize the chamber or disconnect house from the system. Either way you will complete the mission.
Return to Caesar for your next quest.
Caesar, like the other New Vegas factions, wants the Boomers on his side. The Volare! quest will make the Boomers pledge their support for you.
White Glove Society
Caesar wants the support of the White Glove Society, headquartered at the Ultra-Luxe Casino. You can win their support by doing the Beyond the Beef quest.
Brotherhood of Steel
Caesar wants you to destroy the Brotherhood of Steel in Hidden Valley. You do not have the option of convincing the Brotherhood to join Caesar.
Go to Hidden Valley and enter the bunker. There are three leaders (Taggart, Hardin, and McNamara) who have keycards. Use the keycards in the VR chamber on level L2 to start a self-destruct sequence and blow up the bunker. You can get the cards by pickpocketing or by killing the leaders. If you have a 100 science skill, you can hack the VR chamber without the keycards.
Because this quest requires you to kill the Brotherhood, you’ll lock off their quests. If you want to do the Still in the Dark quest or Veronica’s character quest (I Could Make You Care), do them before you start killing off the Brotherhood.
This quest is similar to the NCR quest You’ll Know it When it Happens, but from the other side. Instead of protecting the president, this quest asks you to kill him.
Et Tumor, Brute?
When you speak with Caesar this time around, you will learn that he is ill. There are two ways to go about this quest.
Veni, Vidi, Vici
This is the final battle for the Hoover Dam. You must fight your way into the dam. Once inside the dam, you will have to fight through all five power plants. The fight isn’t complex, but it’s not easy either. You’ll want your heaviest weapons and some really good armor. There are water sources in the dam, but you’ll still want plenty of healing items.
When you finally find NCR General Oliver you can either kill him or convince him to leave. Attacking him starts a big fight against him and his heavy trooper guards. If you have a speech skill of 100 you can talk to him and he will retreat. Either way, you will complete the quest and finish the game.