I used to have some vauge concepts about reincarnation, though I never really took it very seriously. Indeed, I mostly used my concepts as a counter theory to those who tried to discuss it seriously with me in my university days...
For a bit of fun - my loosely defined theory (in a nutshell) was that for the most part when someone dies their 'soul' - being that of a member of the faceless herd - is rather weak and diluted to begin with and soon after death is recycled and reabsorbed back into a general morass of cosmic 'soul soup'. At some stage in an embryos gestational development, a trickle of this crap is drawn in by the new body (or something like that, you get the general idea) and on and on it goes ad nauseum... (Pointless yes, but in accordance with the general law that enegry cannot be destroyed, only transformed).
The exception was that those with a strength of will and forceful, confident personality were able to 'hold it together' long enough to make it into a new body with their basic personality more or less intact. It had nothing to do with being good or 'karma' - just a survival instinct that would see them inhabit and possess a forming human body that, from their limited dead perspective, seemed to offer reasonable conditions for another enjoyable life (i.e. good DNA, etc).
It was a fair bit more elaborate than that, with quite a few other deviations possible, but it worked for me. However, more importantly, when I wheeled it out it stopped the new agers in their tracks almost better than a .45 Magnum would! (the funniest thing was when they actually started to believe it - they had to figure out how to get a personality! Haha).
From a practical view point, even if my old tongue in cheek philosophy WAS true - it wouldn't interfere with my earthly indugences here and now. I'd cross that that bridge when I come to it, and find another body to play in.
P.S. I don't believe in this any more than I do the rabbit with the lollypop theory, which is certainly more colorful and enticing than getting callouses on the hands playing a freaking harp for all eternity... Gah!