Skyrim:Deceiving the Herd

Quick Walkthrough
# Speak to Feran Sadri.
# Read incriminating letter to determine city of victim.
# (Optional) Make it a public kill while wearing at least one piece of Dawnguard armor.
# (Optional) Choose a high profile victim. 
# Kill a victim in the streets, where you can be seen. 
# Plant the incriminating letter on the corpse.
# Return to Feran Sadri for your reward.

Detailed Walkthrough
When you speak to Feran Sadri, he will complain that the Dawnguard have been recruiting and give you an assignment to give them something else to worry about: "You are to make a public show of murdering someone. Do it in the streets for all to see. The higher the profile the better. Make it seem you are a member of the Dawnguard, thus sowing confusion among the herd. Wear this armor and plant this note on the victim." He will give you a set of Dawnguard armor so you can impersonate the Dawnguard more easily, as well as the note to plant on the victim's body. 

Feran will choose the city for you, but you are given the option of what to wear, how to kill the victim, and which victim to kill. After killing the chosen victim, plant the letter on their corpse and return to Feran.

The following table lists only the victims which count as "high profile" for the quest. 
 
 
 
 

Notes
Killing any NPC in the streets will progress the quest, even a guard or random encounter spawn.  The quest as a whole will be completed successfully as long as you plant the letter on the body.
NPCs killed in an interior cell will not count towards quest progression.
Wearing any Dawnguard armor satisfies the quest's optional objective requirement for framing the Dawnguard—it is not necessary to use the armor given by Feran.
Feran refers to high profile victims as ''"...an important member of society. Someone attached to the Jarl's court, a merchant, a bard, a priest, someone with stature."'' However, some of those mentioned will not count toward the high profile option, so be sure to save beforehand if you want to make sure you get the benefits of this.
Reanimating a high-profile target and killing it (again) within the required city will satisfy the high-profile optional objective.
Reanimating Cicero (using Dead Thrall), taking him to the required city, and killing him will satisfy the high-profile optional objective.
Reanimating the corpse named "Peddler" from the unmarked "Peddler's Misfortune" location north of Sunderstone Gorge, taking him to the required city, and killing him will satisfy both the high-profile optional objective without counting as a crime, inciting guards or bystanders to attack nor incurring a bounty. If Markarth is the required city, it is possible to do this using spells with shorter duration than Dead Thrall.
A murder with witnesses will result in a bounty even if you frame the Dawnguard.
Killing Calixto Corrium in conjunction with solving the Blood on the Ice murders will fulfill both quests without incurring a bounty if he is first lured outside the Palace of the Kings.
A bounty can also be avoided with a stealth kill or by killing in self-defense as self-defense is not a Crime.
Avoiding the bounty seems to always fail framing the Dawnguard even if the armor is worn and the kill witnessed.

Bugs
 
The following people are affected by this bug and only count as high-profile targets if the UDGP is installed.  
 
 
 You can use   to fix this once you have gone through all the vampire quests.
 Another fix is to get some fortify pickpocket potions or armor and pickpocket the Incriminating Letter from Feran Sadri and then place it on the victim's body.
 
Reloading a save from before entering the city should fix this.
Read Incriminating Letter to determine city of victim.
Wait for quest messages to appear before planting letter.
Submitting to the guards and paying off the bounty (if one was incurred) should also fix this.
 
 

Quest Stages