Choosing a keyword with good volume, but not too much volume
Check Out the Competition
The domains and URLs - How many are exact match domains? Does every URL in the top 10 include the keyword?
The titles - How do the title tags incorporate the keyword?
The type of content that's ranking - Product pages? Blog posts? Videos?
The types of businesses that are ranking - Are they huge brands? Small businesses? News sites?
How authoritative those sites are - You can use a plugin like SEO for Firefox to check the age of the sites in the top 10, the size of their link profiles and so on.
You're looking for ways that you can differentiate yourself.
Consider Intent
The more specific the keyword (think long-tail keywords), the easier it is to gauge the searcher's intent, and the easier it will be to serve up what those searchers are probably looking for. In search marketing, "intent" is our best guess at what the person using the search query really wants.
Conceptualize the Content
Next, form a plan for the actual content you're going to create that will - hopefully - rank for your chosen keyword.
There are many paths to ranking for a keyword, including but not limited to:
An article
A blog post
A product page
An index or directory of links (to other pages on your site or around the web)
An authoritative guide
An infographic
A video ............!