[rwmj]

Back in the mid 2000s I part-owned a start up company and we made a reasonable living going around telling people pretty much the contents of this list (except for the backlinks stuff which is spammy). Good to see some of it is still relevant. I would add a couple more (from back then - don't really know if they're relevant now):

* Lightweight, accessible website mostly implemented in as close as you can get it semantic HTML. (We used to say, possibly inaccurately, that search engines are like blind web users - make your site accessible, and you're helping blind users and search engines).

* Read your log files. For every customer I used to ask for their log files, and then I'd read them. Very interesting insights can be had about how people find the site and where they go which is more difficult to see from tools. If possible I would spend a few hours tailing the logs live.