Be clear about your motivation. If you are using the letter as an excuse to continue a longstanding feud that caused the divorce or if you harbor thoughts of renewing the relationship, think twice about writing. You may get more than you expect in return.

Stick to the facts once you've got it clear in your mind what you need to communicate. Be clear and specific if you have any requests. Leave out any editorializing if you are just passing on information.

Sleep on it if you have time. You may have spilled some emotion into the otherwise sterile communication that you meant to send. You might even feel better after putting your feelings down on paper. But you may not want to send that particular letter once you reread it the next day.

Keep copies of your letters if they carry any information that could be used against you in court or if you are in a volatile situation where you may need proof to support your allegations.

Use a letter to try to reconcile if that is your motive. Take your time and write it over several days, making sure you own your part in any problems and letting your ex know what actions you have taken to correct your mistakes. Make it a love letter, if that's your goal, and give it all you've got without pointing any fingers.