• Choose the right kind of blogging platform - You can either install something like Wordpress to the back end of a domain you own, or you can go down the road of a free hosted blogging platform. There's a great roundup of the pro's and con's of all the choices on Problogger. It's very important to think long-term when you make this decision because it can be difficult to move things around in the future. For example, put your blog on a free platform like Blogger and you can't 301 pages if you ever choose to move.
  
• First impressions are vital - You don't have the clout to get away with dodgy code or bad spelling; make sure everything is as good as it possibly can be in those first few weeks of your blog.
• About page and welcome page - Rather than using that awkward 'first post' to explain who you are and what your blog is about, put a couple of static pages up with some authoritative and friendly information about, well, who you are and what your blog is about. After the post that attracted me, these pages are usually the first place I'll go on a new blog.
• RSS above the fold - Doesn't need much explanation. I do not want to have to search for that icon when I land on a blog.
• Offer email subscription - Old-school? Still absolutely worth doing.
• Be clever with your language - As per this excellent post on Copyblogger, think about your users and the kind of language they'll connect with. If your blog offers free tips or advice, then why not put that as a call-to-action rather than 'subscribe' or 'sign up'.
  
• Social Media buttons - These aren't right for everyone, but if you're going after the social media crowd then it's worth having a think about how those buttons can be best implemented on your blog. There's actually a fair bit of debate around this in the blogging community...
• Check that on-page SEO best practice is adhered to - You know the rules. If you don't, learn them!
  
• Check theme across different browsers - I spoke to our developers about this and they reckon that manually testing in each browser is the best plan. If you don't fancy that, I've heard some good things about Browser Shots.
  
• Install analytics package - There are free and paid options. Just make sure you've got something (like Google Analytics) up and running from day one.
• Get some feedback - Ask a friend to have a look at your blog before you launch it. It's really hard to spot the most obvious of mistakes when you're too involved in something so use a friend to get some perspective. You could also ask for some advice from forums or blogs in your niche. As long as you're open about what you're after, people will generally be very helpful. This has the added perk of informing a new group of people about your upcoming blog.
  

Blog Launch

You've got everything sorted and you're champing at the blogging bit. Here are a few things to take care of on launch day.

• Launch with at least 5 quality posts - If you're link baiting for those first visitors, make sure you have some other content for them to read on the blog. A blog with one fabulous post can seem like a one-hit-wonder. Ideally, you want your visitors to feel like they haven't even got time to read everything in one sitting; they'll be forced to bookmark you and return another time.
• Submit to directories - Once you've got this first content up, submit your blog up to a few directories. Here are three good places to start:
  
  1. Technorati
  2. BOTW
  3. Blogged
  4. Bloggapedia
  
  If you want to read more about this, take a look at this post on SEJ.
  
• Use Your Contacts - Friends, “friends”, followers, family, contacts... anyone who has ever expressed a passing interest in your life will not object to you telling them about your blog (as long as it has good content on it).
• Use blog URL in email signature - ...make it catchy.
• Get some comments going ASAP - I'm a huge believer in the concept that conversation begets conversation. Get a few comments up on your posts from friends and family (encourage, cajole, threaten, bribe- let your opinionated aunt be opinionated) and watch the party start. Rand has some alternative advice on this (point number 6).
  
• Consider buying some advertising - Bid on a few keyphrases or buy some Stumble Upon traffic. There's no shame in this. It can be really hard to get your content in front of the right audience, and buying some advertising will really help.
• Is it real news? - If you, or the company or person you're blogging for, is well-known, there's a good chance that a blog is news. You can go old-school or new-school with this: either publish a Press Release and get it on the wires, or contact a top blogger or three to let them spread the news for you- or both!

I've steered clear of advice on how to promote an existing blog in this post, but it's worth just touching on how important outreach is from day one. Commenting on others' blogs, offering to guest post (or inviting guest posts on your own blog), participating in forums, responding to any feedback or comments you receive.... all of this is hugely important in establishing your name and brand online and should be included in the first (and all following) stages of your blog launch.

I'm sure you'll have lots more ideas about how to give your blog the best chance of succeeding from launch day and I'd love to hear about them in the comments.