SEO Best practices website design

Hi,
I'm no stranger to web design. I haven't done much of the actual coding but I do a lot of the technical documentation to hand to a developers/designers. This includes wireframes and all website elements, functionality and useability options.
I'm moving into web marketing, and I know a lot of the main seo techniques and basics. But I'd really like to know the best practices for the nuts and bolts of seo.
I'll list what I've gathered from various sources and perhaps people could add their own findings or dispute mine or anything else you like.
Meta Tags
Title Tag = Use around 10 words to write a keyword-rich title that's relevant to the page. Try to start it with your primary keyword.
Description Tag = Use around 20 words (170 characters). Often used by search engines as the description of your site. Should contain a good sprinkling of keywords.
Meta Keywords Tag = only displayed in code and specifically designed for your keywords you can list them up to 744 characters.
Heading Tags = Make sure to use your keywords in heading tags. H1 having more priority than H2 etc.
Alt Tags = for your images. Use keywords to describe all of your images

Other best practises that seem to be strongly recommended on the internet.
CSS = Probably the most recommended of all.
I've also read that CSS can be used to "Order" code as in placing all the keyword rich html at the top, so when the spiders come looking, they crawl it first. Anyone know anything about that?
Drop Down Menu's = Use drop down menus, as they essentially create a site map on every page and this helps the google spider crawl your site.
The site that mentioned this to me, didn't use drop down menu's themselves. So is this one true?

If anyone has any ideas or input please add your comments.
I will be looking for web developers with good SEO skills as well. I will post in appropriate threads though.