I suggest you acknowledge your role in the marriage's failure. Don't accuse your spouse of doing this and doing that.
Sometimes the news that you want a divorce comes as a surprise, and sometimes not. People are often so scared and inhibited about their unhappiness in their marriage that they have not made it clear they are at the end of their rope. On the other hand, you may have sent clear signals that you were miserable, but your spouse was in such denial that they couldn’t hear or understand.
Hence, divorce is often broached in an oblique fashion. You might even finish the conversation with your spouse unsure of whether you made yourself understood.
So listen to your spouse. Most people have great difficulty doing this. It's hard to be empathic if you can't stand each other any more. But don’t argue in a way that puts your spouse on the defensive. It's OK to acknowledge their (and your own) feelings of sadness or shame, but remain firm in your intent to go forward.
Saltz also recommends consulting with a lawyer before initiating the conversation, and if you don't feel safe with your partner or some sort of violence has played a role in your relationship, have the conversation in a public place.
Ending a marriage may not be easy, but sometimes it is necessary. Don't shy away from this conversation. If you need more resources or tips on how to begin the process of your divorce, Family FindLaw offers a wealth of in depth legal information.