There are practical things you should do and things you should know. Some items apply to every divorce, but not all of them do, so just use those that apply to your own situation. Some are best done before the divorce is even announced, some will be easier before you separate, but all should be done as soon as you can manage.
Mutual acceptance of the divorce.
Perhaps the most common source of conflict is when both spouses have not agreed to divorce or at least accepted the idea. Unless you are planning a surprise attack or a sudden departure (a good way to start a war), take time to work on mutual acceptance of the divorce. Starting off on the right foot is the best thing you can do to guide your case toward a smoother more peaceful resolution. Read my article, The Good Divorce
Have sensitive mail sent somewhere private—your office, a friend's address, or get a mailbox at a local mail service center that allows 24 hour access.
If you use a shared computer and want some files to be absolutely private, Google "encrypted folders" with the name of your operating system and read some of the articles, or ask a teenager or a techie friend to help you create and use encrypted folders.
While you have the chance, make photocopies of every family financial record you can find as you will need to know about all family assets and debts. If you used one, visit the family accountant and get copies of tax returns and records for the past several years.
If you will need more income after separation, think about ways you can earn it. Think about getting more education or training to prepare for a better job. Think about ways to reduce family costs..