As the author of my once and future "Faded Glory" (an awesome campaign setting, unrepentantly stolen from Old One), I have a few tips that I intend to use when we resume the campaign in a month or so:
1) Write up the posts as soon as you possibly can after the session takes place. Your recollection of the events will be freshest soon after the game and you are more likely to be able to include the little details that really made the session great. If you don't have time to write the whole thing, write a brief outline of how it went. But...
2) Don't start posting your Story Hour right after you've written the first post. I would say that you should continue to write up each session soon after it happens until you have about 5-6 in the can. THEN post the first post of your Story Hour. It would be hard to overstate the advantages that this would offer (at least to me).
First off, at the start of a campaign, sometimes character personalities, or at least the ways in which those personalities tend to manifest themselves, will not have solidified. But after 5 or 6 sessions, you tend to know who the characters are much better. It also gives time for the players to have described details about the appearance or background's of their characters that may not have been apparent at the start. This extra level of personality and detail will help hook your readers.
Another thing that helps hook readers is more story. If there's one thing folks like more than a good Story Hour, it MORE good Story Hour. If you have half a dozen session's worth of posts ready to go then you can update more often early on and that will really help to get people interested in what you write.
3) Have one or more of the players help by writing an "after action report" describing what took place in any large combats. I SO wish I had done this from the start. I did it near the end of my last campaign and it was completely invaluable when I finally got around to writing up those sessions. One of these had a combat that went for 33 rounds. I'd have never been able to describe what happened with any degree of accuracy without those after action reports.
4) Have another player or yourself write down any particularly funny, important or otherwise memorable lines that get said during the session. These are priceless and add tremendous interest to the story. For both this as well as the after action reports, give extra XP if it will help motivate the players to help you out.
5) Figure out what conventions you wish to use for things like "out of character comments" or how you describe combats. Personally, I used parenthesis for when I wanted to make a comment as the GM instead of the narrator of the story. I also would italicize the names of any spells that were cast so that they would stand out and be obvious to the reader. I've seen others who use colored text to do the same thing and it helps me keep track of what's going on in the story.
6) Use plenty of paragraph breaks. Nothing will cause me to close a new Story Hour thread faster than seeing an enormous block of unbroken text sitting in the first post. It looks unconquerable.
7) This is just a personal bit of wisdom and you can take it or leave it as you like: Don't write a Story Hour because you want people to tell you how cool it is. Write it because you like to write or because you want a record of your campaign or just to share it with no expectations that tons of people will read it. If you do it for those reason, you will never be disappointed. And when somebody pops in to tell you how cool it is, it'll just be gravy. Everybody loves a little extra gravy, but it ain't your meat and potatos.
8) In case it needs to be said, ALWAYS write your story hour in some other program before copying and pasting into the ENWorld boards. And save backup copies regularly. Also, if you are using a new word processor of some sort, do a test post in another forum to make sure it copies over well. Some programs do wonky stuff like replacing quotation marks with a string of question marks.
Good luck and have fun.