Penelope Trunk has posted The easiest instructions for how to start a blog. It is a great post with six simple steps but also links to additional information once the blog is rolling.

Her list goes like this (read more at her site):
1. Ignore buzzwords.
2. Pick a topic — you can change it when you know what you’re doing.
3. Spend two seconds choosing software.
4. Post something right now.
5. Practice, practice, practice.
6. Ignore your lack of readers.

Since I use WordPress I disagree with her about point 3. The last point (ignore lack of readers) is worth remembering, bloggers write to be read but it takes a while to build an audience.