Just read a nice practical piece on using Reincarnation in 4E by DMG 42. It's pretty good. Here the players actually cooked up a set of rules and convinced their game master to pre-roll their new characters they would eventually reincarnate into if they would die.
So I figured I'd call your attention again to the series.
The Joys of Reincarnation deals with the more practical sides of working with reincarnation of (player) characters in your everyday campaigns. How do you go about it?
The Shock of Reincarnation deals with the role playing aspects. How does it feel to remember - and do you inherit the skills and memories of your previous incarnation?
And The Secret of Reincarnation deals with integrating the concept in your campaign universe - how commonplace is the knowledge, are there brotherhoods or sisterhoods protecting the secret, does everyone reincarnate - or is it a freak magick thing?
Art: by me - the grand Duchess wakes with a shock from a Reincarnation bath
PS Rob Schwalb seems to have a nice post on this too, but I can't check that right now, as his site does not respond. Maybe by the time you read this, you can.