The Hidden Blade Assassin's Creed in Depth

Poetic Justice
Kill the target with the shovel that the man was using to bury his fiancee (or wife... he contridicts himself in the dialog). The shovel is an improper weapon that Ezio carries as a backwards mace, i.e., Ezio points the shovel in the wrong direction, even when sheathed.

The shovel is typically dropped when Ezio starts to sprint, free run, or climb. You can get the shovel to roof level by tapping jump when Ezio is pressed against a wall. Ezio drops the weapon as he grabs the roof above, but the weapon is often dropped near the edge of the roof, which allows the weapon to be picked up again at roof level.

When you spot the target, the camera will zoom to her, and she will start running to a waypoint on the arch above. The game forces you to drop the shovel after the camera zoom, but you can pick it up again. Intercept the target on the roof and kill her with the shovel. If you don't have any other weapon in your sheath, the game will force the shovel into the sheath in the memory corridor, and you will be able to use the shovel later ("Elm Street Effect").

Point Blank Spear
This is similar to the previous clip, except that you throw a spear at close range. You can obtain a spear from a nearby patrol. Get the spear to a higher level by pressing against a wall and jumping. The spear will often be dropped at the edge of the higher platform, allowing you to pick it up again.

Tripwire
The goal is to aim the gun across the target's path and shoot her as she runs across. You can start aiming the gun before you have even spotted the the target.

Parachute Drop Assassination
You barely have time to use the parachute in this mission because the target immediately flees to roof level. To complicate matters, you can't steer the parachute when the camera zooms to the target, so you have to steer quickly before the camera zooms and immediately afterward. Flying with the parachute will also cause the civilians sitting at the nearby bench to stand up. Use this to your advantage... The target will often bump into one of the civilians as they stand, causing the target to stumble. This buys you a few precious moments to drop down from the parachute and make the kill.

Long-shot Poison
In AC2, you lose your lock on the target when he/she is more than 30 meters away. When using the hidden gun, however, your aim on the target is preserved as long as you continue to hold the shoot button. The same is true in AC Brotherhood, for both hidden gun and poison dart.

The target always flees along the path as shown if you start aiming while standing in the same spot as shown. You desynchronize at a distance of 50 meters, but you should shoot the dart a little early (don't shoot at 49 meters) because the target still moves away from you after getting hit.