How Should I Act When Someone Dies?

It has often been a source of much wonderment to me that we have such little insight into an area of life that is common to us all. Perhaps this is a reflection on our society and its particular taboos. But since we all die, and most of us will experience the death or bereavement of one or more people close to us, it's a good idea to consider the most "real" and "honest" way to act when someone dies.