Not to be a smart ___ but the answer to your poll is "all the above".
It depends upon the subject and your ability / knowledge of the website's topic(s). Your ability, skill, knowledge, etc. for creating a website (the coding, SEO, etc).
So, domain name - of course, knowledge or topic/content, way to get it coded (html, php, asp, flash.etc), and hosting.
You need to know your target market - who is going to (who you want to)
read the website? Where are they? Do they use the internet?
What is your competition (other websites on the same topic)?
These are b r o a d topics with a lot of detail to each.
here's a link to check
~ROland