Nice post, Luke. Useful information.
The tips for new buyers are good but, of course, you can never have an exhaustive list. For every 10 new buyers making a purchase 9 are likely going to lose money as sellers have become a very slick lot and very good at passing rubbish off as worthy investments.
My #1 advice to new buyers is to check for profit. If the site doesn't have a history of regular profit - don't buy it. It's hugely difficult to make money with a new site. Much more difficult than most sellers will have you believe. If you're new to this restrict your purchasing to a site that's got a proven business model.
My #2 advice: Don't trust claims of "potential". And don't take the seller's opinion on anything. I did an interview with Canada's biggest newspaper this week in which I said that one of the most common mistakes newbies make is not separating fact from seller opinion. It's a business decision - get the facts, not a glossed up version of them.
Google Analytics can be easily faked. Video is a doodle to doctor - he can simply change his hosts file and all the video is being fed from his PC rather than the Adsense or Analytics site. Backlinks checks etc., don't take into account who owns the linking sites - they could be seller owned and the links could disappear overnight. And it's not easy to do due diligence on traffic stats if you haven't got some experience in it already. Being a buyer is a bit like being the security staff of a US president. You need to be always alert. The terrorist needs to get lucky just once. And when it comes to valuing sites, I've written [an article for Sitepoint that may be worth reading (short version [URL="http://experienced-people.net/forums/showthread.php/4-How-to-Value-a-Website-or-Blog"]here](http://articles.sitepoint.com/article/web-site-valuation-guide)). It wouldn't be wise to rely on a value that the seller gives you, particularly if he got it off some online valuation tool (any online valuation tool, even mine).
But your tips are a good starting point, Luke. I've got more information on things like transfering sites to a new hosting account on my site. We discuss more advanced site selling and site buying matters at the forum in my signature and everyone's welcome.