If you have children or a significant amount of money/assets, you are strongly advised to use a solicitor. A solicitor will:
provide advice on what rights you have and what would be a reasonable financial settlement;
help you negotiate an agreement on financial arrangements and how any children will be looked after;
draft the court documents and file them on your behalf
You can decide on the level of engagement you would like from your solicitor. You can discuss the arrangements with your spouse before filing for divorce if things are amicable.
Please note that both you and your spouse cannot use the same solicitor.