I wouldn't presume to tell you I know. To my knowledge I've never died before and no one I've ever known who has died has ever showed up again to fill me in. Personally I'm Christian with lot of eastern thought mixed in.
I heard this women, Dr Jill Bolte Taylor on PBS on day speaking about her book. I haven't got it yet but intend to read it. Her experience with having a stroke gave her a new persective on what life is about. This video by her is worth watching.
http://www.ted.com/talks/jill_bolte_taylor_s_powerful_stroke_of_insight.html