The following was copied and pasted from here and here, with some adaptations and updated information.
To submit a post is simple. First, your post should be of a Christian nature, but this does not exclude posts that are about home life, politics, or current events written from a Christian point of view, which are welcome. Posts need not be of a theological topic. The Christian Carnival is open to Christians of Protestant, Orthodox, and Roman Catholic convictions. One of the goals of this Carnival is to offer our readers a broad range of Christian thought.
Submit a post using this form (the "Submit a Post" tab above). We no longer take email or blogcarnival submissions.
Please submit only one post (per blog, per author) dated since the last Christian Carnival deadline, i.e. something posted since midnight EST the Tuesday night before the last monthly carnival.
You may wish to consider that the readership of the Christian Carnival will be more varied than your usual readership, and you might do better contributing a post with broad appeal.
Be aware that hosts have the option of limiting the Christian Carnival to the first 40 (or 50) acceptable entries. (Most hosts do not do this, and most months do not have that many posts, but this is a good reason to enter early just in case. Hosts that limit the number of entries can not simply select their favorites, so you can't rely on your post being good.)
You can join the monthly reminder list for the Christian Carnival here. You will receive monthly calls for submissions and notifications that carnivals have been posted. (Note: there was a previous announcement list for the Christian Carnival. That list is no longer usable. This one came into existence around the beginning of May 2007. If you have not joined such a list since then, you are not on the current announcement list.) You can also join the carnival’s Facebook page here. Feel free to post links to relevant blog posts there, but posting there does not constitute submission to the carnival.
When the Carnival is posted, please announce it and link to it on your site. You might say our kind hosts are “paid” for their hours of work by the links they receive on Christian Carnival day.
Disclaimer: As the goal of this Carnival is to highlight Christian thought in the blogosphere, entries will be limited to blogs that share that goal. Posts strictly focused on matters unrelated to Christianity or from blogs with potentially offensive material that Christians may not want to link to may end up being rejected, but there are other carnivals that would be more appropriate for such posts. Though this will be a judgment call on the part of the week's host or the carnival's organizers, and being human they may make mistakes, this is necessary given that the Christian Carnival is sometimes quite large, and it is sometimes questionable whether the entrants are seeking to promote Christian thought. We also expect a level of discourse that is suitable for a Christian showcase. Thus entries may be refused if they engage in name-calling, ad hominem attacks, offensive language, or for any similar reason as judged by the administrator.