Assassin's Creed II/Sequence 9: Carnevale

Knowledge is power
You need to test out the new Hidden Blade attachment Leonardo made from the Codex page you brought him, so head south and hop over the wall to the garden behind it. Go out back to the dock to start pistol training. There are three target dummies, two on docks to your left and right and one up on a window ledge above the dock on the right. Pull out your pistol with the weapon selector wheel, then lock on to a target and hold the armed hand button until you've drawn a tight bead on your target. Release to fire. Take out all three targets, then head back to Leonardo's workshop. The pistol holds six shots, and when you run out you can buy more from a blacksmith for 175ƒ apiece.
 * Memory start: Knock on the door of Leonardo's workshop.
 * Reward: 2,000ƒ, Pistol, Carnevale mask, Assassination contracts unlocked

Damsels in distress
As soon as you're introduced to sister Teodora a murderer will run through the house and you'll need to take him out. He runs away from you from girl to girl and slits their throats if you get too close. Head west to where he's holding his first hostage. Inch up to him until you can lock on, then use your recently learned pistol skill to take him out. It's best to to do it the first chance you get, as later on there will guards nearby you'll have to escape or fight when the memory concludes.
 * Memory start: Knock on the door to La Rosa della Virtù in the Dorsoduro district.
 * Reward: 3,000ƒ

Nun the wiser
Just follow sister Teodora and Antonio to the Squero di San Trovaso. When you get there you'll find out that to win a Golden Mask, which gets you into the Doge's party, you'll need to win a competition.
 * Memory start: Knock on the door to La Rosa della Virtù.
 * Reward: 3,000ƒ

Ribbon round-up
You need to obtain ribbons from the women around the area, supposedly by charming them. Ezio has other skills at his disposal, so you just need to walk around to each of the groups while holding the legs button to steal the ribbons from them. The groups are marked on the minimap with blue objective markers and the ladies don't put up a fight, making this the easiest challenge you'll need to complete for the Golden Mask. You need to collect 25 ribbons in four minutes and the ladies carry small, medium and large bundles of them. When you've got the ones inside the square, head out into the streets to find more groups of women.
 * Memory start: Talk to the man in the northeast corner of the Squero di San Trovaso.
 * Reward: 3,000ƒ

CTF
The goal of the game is to grab the flag and return it to your homebase. If your opponent gets it, you'll need to chase him down and tackle him to get it back. Likewise, he'll be trying to do the same to you when you have the flag. You can get the flag back from the other guy by getting near him for a second or two, by tackling him or by punching him (since you'll meet the first requirement). You win when you've brought the flag back three times, and you desynchronize if your opponent does the same. You start out on top of a roof and the flag is down on the ground directly north of you. Your opponent is on his way from a rooftop to the west. If you want to let the other guy get the flag and cherrypick his base, just proceed due west and slightly north to another curtained stall on the farthest west building, right on the water.
 * Memory start: Talk to the man next to the Santa Maria Dei Carmini, northwest of the Squero di San Trovaso.
 * Reward: 3,000ƒ

There's no easy way to get down to the flag, at least not before the opponent gets to it. By this point you should have enough upgraded armor that you have a ton of health, and even more if you've been collecting Codex pages, but if you're a little low, grab some health vials before attempting repeated jumps down to the flag. From where you start the memory, sprint down the roof you start on toward the flag. Free run across the wooden balcony behind the side of the building in your way, then continue straight on directly at the Santa Maria Dei Carmini (the big white building with the gray roof). You'll jump off toward it, land on the very edge of the building below before falling to ground, which puts you just to the right of the flag and costs two health squares. From here, head directly back south from the flag through the archway to the next courtyard. As you're heading this way, avoid the opponent (he's pretty bad at getting the flag back from you), and you should see some crates on the left side of the next area with white sheets on them. Free run up them, which will take you to the roof via a series of protruding poles. Climb up one more level to your base and head into the white marker.

You can get away with this tactic twice before the game gets wise and the pursuit guard you're racing puts on his super speed. After the first two flags you capture, save yourself the trouble and just head to his base to nab the flag back there. Capture the flag for the third time and you've won the competition and are one step closer to the Golden Mask.