“Writing a devotion can offer hope to your readers and inspire them in a way that lectures or plain articles, may  not. A devotional is a very well thought out piece about one very minute topic usually focusing on a particular spiritual lesson. Writing devotionals does not have to be difficult, there are many steps you can take to calm yourself down, get centered and write what God wants you to write.

Yes!  There is something already inside you that God wants you to say. You just have to open your heart to the Holy Spirit, and listen.

1. Be prayerful — Before you put pen to paper, or rather, start typing, pray. Ask God to tell you what He would have you to write about. What message does He want you to impart? Be mindful of what comes to mind as you are praying. Does a particular person come to mind with a specific issue? Does a specific verse pop into your head? Listen. He will tell you what to write.
2. Pick one topic — After intensely praying about what to write, pick one topic that comes to mind and be very focused on that one topic. It is easy to get carried away writing with all the ideas that will come to you!
3. Keep it short — Your devotional should be no more than one page, or 500 words. But it is even better if it’s less than 500 words, shoot for 250 words to keep yourself focused on one small laser targeted topic.  This will also help to keep your reader interested and with you.
4. Know your audience — When you have your topic, write it to a specific audience, this is known as your “target market” in business, but here, this is your audience. Ask yourself the question:  Who is going to read this devotional? If it helps, write your devotional as if you’re writing it to a dear friend.
5. Check your facts — Make sure, if you are quoting biblical scripture that you not only check the scriptures to make sure you are not taking something out of context, and that you are quoting it correctly, but make sure you are using a relevant verse to support your devotional.
6. Inspire action — Ask the readers to do something at the end of your message in your closing paragraph. That action will depend on what your message was about. You can end with a very short prayer if you wish, but keep it related to the message.
7. Be yourself — Remember to be yourself. You’re not perfect — no human is — and that is perfectly okay. Grammar isn’t as important as your message. Do check your spelling with the spell checker, and have someone else read it if you wish, but the message is the most important thing here.”

[found on http://faithfulbloggers.com/blogging/seven-tips-on-how-to-write-a-devotion]