Does anyone know the best way to trigger this quest? On my other two characters it worked fine, but I had no interest in the quest reward due to being a Warrior and an Assassin. This time though I'm a mage so the reward will benefit me, but the quest just will not start!

I arrived in Windhelm for the first time on this playthrough at roughly 8:30am. During the daytime I spoke to every NPC available then headed to Stony Creek Cave for a misc quest. By the time I finished the quest it was around 10pm, so I fast traveled to Windhelm and got there around 1am, which I thought was good timing for the Blood On The Ice quest. So I walked to the graveyard, and nobody was there.

I headed to Candlehearth Hall to find Susana The Wicked still alive and walking around the Inn.

I then left the City and came back a day later at around the same time, but Susana was still at the Inn.

Does anyone know what I have to do to trigger this damn quest!? Typical that it doesn't work on this playthrough when I have a real interest in the Necromancer Amulet!

According to the http://www.uesp.net/wiki/Skyrim%3aBlood_on_the_Ice#How_to_Start_the_Quest

This quest is triggered by a counter that starts at the beginning of the game which will increase each time you visit the city of Windhelm or the immediate surrounding area. When it reaches four, the Blood on the Ice quest will be available, although two more conditions must be met:

• The player has to enter Windhelm, either through the main gate, the docks gate, or by fast-traveling, between 7pm and 7am. The graveyard scene should then be triggered and the quest ready to go.
  
• Tova Shatter-Shield and Anvanya need to be alive

The easiest way to trigger the quest is to walk back and forth between Windhelm Stables and Brandy-Mug Farm two-three times, then enter Windhelm between 7pm and 7am. If the graveyard scene is not triggered by this, there's little hope you can trigger the quest at all.