The host's job is to promote Christian unity first and foremost by making sure the Carnival stays civil and making sure the discussion isn't hijacked or blogswarmed by any one group or topic. The host retains the right to decline posts at his or her sole discretion, whether for the tone of the post or because too many submissions have been on the same topic for the same month. While it is expected that each host will have his or her own distinctive views, the host blog should be generally courteous to those of other views. That's to say, if your blog's usual topic is "Why Everyone Else Is Wrong", I'd have to respectfully decline the hosting offer. I say this only to head off future trouble; this Carnival shouldn't be hosted at why_everyone_else_is_wrong.com.
The host should announce the Carnival with a reminder announcement at least a week before the posting deadline. The announcement should include the deadline for submissions and the intended post date of the Carnival. If the host wants to promote a topic of the month, that should be announced also. The host has some discretion in setting dates, though generally the Carnival will take place around the turn of the month each month.
If you are interested in hosting, please drop an email to the Carnival address along with a month that would work for you, e.g. "end of March" or "end of April".