If you are interested in having David speak at your church, conference, or other event, send an email here.
If you have a comment or question about one of his blog posts, just write in the comments section of the particular post. (Be sure to look at the Rules for commenting page.) Keep in mind that there will be a slight delay with comments as they await moderation and approval.
If you have a question for David, go to his FAQ page and post your question in the comments. (If your question or comment is personal, email him.)