In order to avoid potentially expensive problems down the line, details of the allegations in the petition should be shown to your spouse and, if possible, agreed. For example, if the respondent takes exception to an allegation of their unreasonable behaviour they may choose to defend the divorce (see below), which would result in considerable expense and delay. I would recommend sending them a copy of the whole petition, as this may show up any errors in the document, which would otherwise involve a costly application to the court to have the petition amended after it is issued. As indicated above, if you need the respondent to admit adultery or to consent to the divorce, these things will need to be agreed before the papers are filed, in any event.
You may also reach an agreement with your spouse as to who will pay the costs of the divorce or as to how those costs may be divided between the parties.
The statement of arrangements for children form should also be sent to your spouse, for them to sign if they agree with the arrangements that you propose. If they do not agree, the form can still be filed with the court signed only by the petitioner, although the respondent will be given the opportunity to file their own form and the court may well then direct that the divorce cannot proceed until matters have been resolved – hence arrangements should be agreed if possible before issuing the divorce