Let's be clear here. I'm not referring to overall (home page) blog SEO. Whenever you write a new blog article, you optimize it for the search engines or perform SEO…at least you should be, but that's another post.
Here's my list so far; this is what I do *per post*, in no particular order…
1. Linking - Internally to other relevant articles on my blog(s)/Externally to related articles on other blogs – I consider both SEO, others might not.
2. Bold/Italic/Underline words & phrases where appropriate – I've heard this helps, but others may not think so.
3. Change the Permalink; remove unnecessary words. For reasons I don't completely understand, the accessible best Permalink URL format is not a default in WordPress. Many blogs have dates in the URLs or other extraneous words that make your URLs too long and hard to remember.
4. All in one spot, I take care of Mata Description, Title, and Keywords – Yes, both Google and Yahoo have stated that they no longer use meta keywords for anything, but if I have time, I may still input them for smaller engines.
5. Tags. While somewhat separate from the keywords mentioned in #5, it is still essential. Thanks to my good friend for reminding me of this in the comments below.
6. Optimize Images as applicable. You need can resize, compress, and optimize your image files
That's all I do to SEO an individual post, although I feel I forget something. Anyhoo, What do YOU do…is there more to do?