I know it's an old post but to answer the original question in England &
Wales under the solicitor's Family Law Protocol it is considered good
practise to notify the respondent of the intention to commence divorce
proceedings.
It may avoid unnecessary disputes (which can be
costly in terms of both money and time) if the respondent has sight of the
reasons given for the marriage breaking down before receiving the
petition. When there is objection to the reasons they can be
negotiated into something less controversial. Also agreement about costs of
the divorce can sought so there are no nasty surprises to inflame the
situation later.
A
separation agreement is
something different and documents the financial arrangements spouses may
wish to make when separating.