With a recent death in the family we took an approach the related more of their personality - their influence on other members of the family, etc. She was a "behind the scenes" type of person who made other people shine and was very comfortable with that. Another obituary on the same page was written in the first person - it was different and I also like it.
I was surprised of what information we were unsure of - places of events, dates, etc. I don't think there is anything wrong with putting together some of the basics in advance.