Miss Wicca's right about detail, so here's another one for you to study ^^" (Yes, it's one of mine xD)
She sat in her darkened apartment, the only light being the moonlight filtering through the window and the snow coming down in the dark sky outside. She was dressed only in a small, knee-length black dress, sitting on her bed, with her knees drawn up to her chin. Her raven hair covered some of her face, the rest falling to just below her shoulders. Her pale skin looked pure white in the moonlight, and her silvery/ice blue eyes were covered by her eyelids. They snapped open, and she slid off the bed, closing the curtains, so she was in complete darkness. He'd gotten her letter, and as was her duty, she had to start her revenge - first, by taking out his friends and family. She didn't want to, but as the eldest daughter, it was her duty. The only thing that seperated her, and the rest of the assasins in her family was that she didn't share their bloodlust. Turning on the lamp on her bedside table, she changed clothes, into a dark jumper and jeans, and tied her hair up out of her face, into a bun. Pulling on a hoodie, she zipped it up, and pulled up the hood, hiding most of her face, with only her mouth visible. She slipped a knife into her pocket, and her second note, as well as lipstick, before turning off all the lights in her apartment, and leaving through the fire escape. Most people would think she was asleep. Coming onto the street, the snow crunched under her boots as she made her way to her first destination.
*
About an hour later, she laid the man's corpse on his bed. He had been living alone, which was a relief. She had cleaned away most of the blood from when she had cut his throat and threw a blanket over him, bringing it to his chin. No-one would discover him until the following morning. Taking some toilet paper, she cleaned the blood from her hands and the knife, before pulling the lipstick from his pocket. Going to the mirror in his bedroom, she wrote 'Por Siempre' on the mirror. All the killers of her family had used the phrase, on everyone except their mark. They didn't have to, because normally the marked's body was lying at the bottom of the docks. Most of them hadn't been recovered. Cleaning the blood from the floor, she made sure everything was tidy, before leaving. Finding a postbox, she slipped the note into it. He'd get it in the morning. It was just like the last. A picture of her, the exact same as he had recieved before, with lyrics to the next part of the song. That was how they all did it, though no-one had ever reported having the cards, nor had the cards ever been found - they were always recovered after the target was killed, to be used for the next one. Returning to her home, she placed the clothes she'd worn at the back of the wardrobe, and slipped into bed, quickly falling into a dreamless sleep. Now all she had to do was wait until morning.