The Hidden Blade Assassin's Creed in Depth

Drowning the boy does not stop him from crying, and you can still initiate the cutscene after he's gone. This grab-move exploit was originally reported by aurllcooljay. Both he and I independently managed to kill this boy in this way. This is the first published video of a child dying in the Assassin's Creed series.

Blitz
You will desynchronize if you kill you Silvestro before he reaches his destination. Since you already know where he is headed (it's already marked on the map), you can have your gun ready when he arrives. Shoot when the red targetting icon appears over his head, or when you hear him start talking.

Thrown Heavy Weapon
The way the game computes your distance to the target is a little weird in this mission, and I'm still not sure exactly how it's done. (For example, it could be the average of your 6 targets.) I throw the axe at a reported distance of 17 meters; any farther and the axe will pass through him. Typically, thrown heavy weapons or spears will work up to 20 meters. I think that is still the case... I suspect that it is the "17" meters that is reported incorrectly.

Mini Parachute Air Assassination
You barely have enough room to pull out the parachute. I find it helpful to start the jump at the very edge of the platform, which is why you see Ezio look down over the edge before jumping.

39 Meters
Start by superblending so that you can rapidly eliminate all of the guards in the area. Disarm Silvestro in a location where there are no dropped weapons for him to pick up. Since he is left with nothing to fight with, he becomes demoralized and will run. Find a clearing, lock on, and hold down the shoot button. At a distance of 30 meters, you will lose the lock on the target, but your aim is preserved. Fire the shot before the target is 40 meters away, otherwise you desynchronize. As I mentioned ealier, the game calculates the distance in an unusual way in this mission, so you'll need to be careful.

Parachute Eagle Strike
Grab Silvestro and drop him over the edge of the cliff so that he lands on edge of the roof and then stumbles to ground level. The roof breaks his fall so that he doesn't die. In this video, he didn't fall to ground level, so I "push" him over with a throwing knife.

When you reach the top of the tower, aim the jump by putting the red targeting icon in the middle of Ezio's head. Time the release of the parachute by watching specific structures and textures scroll off the bottom of the screen. Grab the edge of the roof to keep Ezio from dying, and air assassinate.

Silvestro kills his own dumb self
Your opponents will chase you as you jump between the overhead platforms. If they land right behind you, they won't have enough room to stand and will fall to their deaths. In this video, I actively try to eliminate all of the guards first, but Silvestro's stupidity manages to defeat me. I have to kill the last guard after the memory corridor.

Even after killing the target, you can restart the assassination mission by desynchronizing. This is rapidly achieved by killing the woman that Silvestro was conversing with.