The Hidden Blade Assassin's Creed in Depth

Anonymous Blitz Assassinations
Run full speed to the corner of the compound and then continue along the wall to avoid detection. Climb on the nearby roof to get over the compound wall. As you enter the compound, there will be a scripted line, "Men, prepare yourselves..." This does not mean you are Exposed. On the contrary, the game forces your status to Anonymous at this point, which is why you see a flash as Ezio goes over the wall. Enjoy this amnesty while you have it - Despite being in a restricted area, Ezio will not be Notorious inside the compound until you hear him say, "I need to find a way to open the gates." Forget the gates. You don't really need to open them, and it would only slow you down. Continue running at full speed to the target to avoid detection.

You can assassinate the target even faster by going over the main gate. Ride a horse to get there quickly, and use a smoke bomb to avoid becoming Exposed as you climb. When you reach the roof of the gate, don't pull yourself over yet. Instead, slide left just a little before pulling yourself up so that the archer on the right does not see you. Jump into the compound and head straight for the target. Don't worry about being seen. You can kill Francesco before your amnesty expires.

After the assassination, you'll return to find the gate opened. Your mercenaries will enter and engage in a fake battle with the guards. I say "fake" because everyone just stands around looking at each other, as opposed to fighting. This glitch is probably caused by killing the target prior to the expiration of amnesty.

Blitz Assassination
Since you automatically become Anonymous when you enter the compound, you may not care much about being Anonymous beforehand. If you have better aim than I, you might be able to dismount off the horse directly onto the compound wall so save a split second. When you reach the roof, you don't need to slide over. Again, just jump down and enjoy your amnesty.

Air Assassinations
You can air assassinate from the main gate roof. Or you can approach from the main building, although this requires you to clear out the guards first. Use you double hidden blades wisely. Francesco walks around in a loop until he sees you, but part of his path is under a covered area. Just wait for the right moment. If you prefer, you can use throwing knives from these vantage points instead of air assassinating.

Stunt Assassination
From the roof of the main building, jump down and kill him as he goes around in his loop. Don't worry about the haystack. You can't reach it from the top of the building.