Having done this myself several times I'd encourage you to write down what you do believe.
- Use only positive terms
- state what you do believe, not what you don't believe
- keep it what you personally feel is truly important
- make it a 'testimony' - in other words, it should also tell a story about the difference it has made in your own life (after all, if it hasn't really made a difference to you, in the way you live, why would you think it's important enough to tell other people?)
In coming messages to this blog I plan to do just that - give you my own statement-of-faith / testimony.