Assassin's Creed II/Sequence 3: Requiescat in Pace

Roadside assistance
You start the sequence on the road to Monteriggioni, heading toward Villa Auditore where you uncle Mario lives. Run along the road with your family until you run into Vieri de' Pazzi and his gang. Take out the guy that comes for you with your hidden blade, then the one accosting your mother and sister. They're both unarmed, so they should only take one hit to kill. After that your uncle shows up and gives you a sword. Take out the rest of Pazzi's men while protecting your mother and sister. It shouldn't be very difficult, as the bad guys are mostly distracted by your allies, so it's fairly easy to either assassinate them from behind or hit them with the sword.
 * Memory start: Automatic
 * Reward: 250ƒ

Casa dolce casa
Follow your uncle up to the front of your villa, and he'll give you 1,995ƒ to go outfit yourself at the town shops. Go back down into town and buy Leather Greaves and the Dagger at the blacksmith, then head over to the healer and buy five medicine vials.
 * Memory start: Talk to Mario at the entrance to Monteriggioni.
 * Reward: 800ƒ, Medicine Pouch, Dagger, Greaves

Practice makes perfect
Mario will teach you some combat moves out in front of the Villa. Perform one quickstep, three counters, three taunts, three escapes, then beat the trainer in a live fight. When you're done, go back to the room Mario was in to learn that he went off to kill Vieri de' Pazzi. Before you follow after your uncle, go upstairs and talk to your sister and mother. You'll now be able to put feathers into the chest in your mother's room.
 * Memory start: Talk to Mario in a back room of the Villa.
 * Reward: 1,000ƒ, Quickstep skill, Counter Kill skill, Taunt skill, Escape skill, Courier assignments unlocked, Races unlocked

What goes around
Grab a horse at the gate into Monteriggioni and ride southeast to Tuscany, then to a couple small houses outside the city walls. Start by following your uncle up to the city walls. Equip the throwing knives your uncle gives you from the weapon selector wheel, then climb up to the marker on top of the wall via the crates at the bottom. Lock onto the first target and hit the armed hand button to throw a knife. Run to the guard's position, then lock onto the next guard and throw one at him too. Go down into the courtyard in front of the gate and lock onto and kill the last guard up on the roof before opening the gate for your uncle. Depending on how fast you got the gate open, you may need to help them take out the last of the guards outside.
 * Memory start: Talk to Mario at some houses outside the city in Tuscany.
 * Reward: 2,400ƒ, Knife Belt, Codex page, Letter to Franceso de' Pazzi, Knife Throw skill

Follow your allies when they get inside the city and your uncle will tell you to distract some nearby guards for him. Take the four mercenaries he gives you and head up to the enemies. Lock on to one of them, then press the head button to send your allies at him. While the guards are distracted fighting the warriors, walk up behind them and assassinate them. Afterward head to the Santa Maria Assunta and talk to the wounded soldier sitting by the well. Avoid any guards along the way or you'll have to fight them (your warrior allies can't help themselves). The man says your uncle is under attack, so head over to the nearby fight and help him out. Mario tells you to go find Vieri, and you can go straight to it or stay and help him clear out the ambush. Either way, you'll want to head to the northern gate and enter the marker on a rooftop nearby.

After a cut scene, Mario will arrive with his forces and start fighting the Pazzi men. Across the courtyard on the rampart at the city wall is Vieri, your assassination target. It's best to approach him from behind, which means jumping down to the roof on your left and then to the wall and climbing up the rampart behind him. He somehow senses you as soon as you climb up, but it'll be just him and a couple of his guards to start, and he usually throws the first strike setting you up with a quick counter kill to end the mission.

A change of plans
Follow your uncle back into the Villa, then head into the back room with the codex pages on the wall. After he explains about the codex pages, climb up to the top of the Villa and interact with the viewpoint up there (or synchronize it if you haven't done so already). You have to collect four codex pages around Monteriggioni, and they're now revealed on your map. You get codex pages by looting boxes. The pages are very easy to find, as they're marked on your map. The ones in the city are in dead end alleys, but just set a GPS marker on them in the map and you should have no trouble finding them all. As soon as you get the last one, the memory will be synchronized.
 * Memory start: Head into the marker in front of the training area in front of Villa Auditore.
 * Reward: 800ƒ
 * 1) Close by the southeast corner of the villa, it's down over a wall right by where you land if you do a leap of faith from the viewpoint.
 * 2) In the southeast quadrant of the city, just south from the first codex page.
 * 3) On the opposite side of town from the second codex page, almost directly west of it.
 * 4) The last one is outside the city, far to the east. Take a horse from the main gate and ride out there.