Watch the complete Dexter Showtime series a few times.
If you really know the person then you will know his enemies, frame one of them.
1. watch the following on body decomp (if you want him/her to vanish):
http://video.google.com/videoplay?do...perfect+murder
2. learn how to pick locks, so you can leave evidence in your marks house or apartment
3. learn both your victim and marks habits and routines, pick the right time when the mark will have no alibi
4. Kill your victim at his home around 4am, leather pouch full of ball bearings to the head while sleeping, then a hypo full of over the counter poison or just a slip knot zip cord around the neck
5. bury at night at one of your marks relatives back yards or farm would be best.
problems, if both or either mark or victim sleeps with someone every night.