To optimize for the "I'm feeling lucky", simply ad those words to the beginning of your page title. Instead of calling a page, “Blue Widgets by the ACME company”, your page would be titled, “I’m Feeling Lucky: Blue Widgets by the ACME company.”
When users type in a search term, i.e. "blue widgets" and click "I'm feeling lucky", your optimized page has a 300% better chance of being the lucky result.
Actually, the I'm Feeling Lucky simply takes you to the first result. This entire forum is about trying to optimize your site. If you get the #1 listing - you have the "I'm Feeling Lucky" result.
As a side note, I used to think that it was a random result from the listings...
You can estimate how many "I'm Feeling Lucky" hits you get by looking at how many of your referers are exactly "http://www.google.com/" (with or without a slash, but with nothing after). You cannot tell what search terms someone used to reach your site with an I'm Feeling Lucky search because the referer does not contain the search terms. (Try 'webmasterworld blue widget' - Webmasterworld will highlight the search terms if you click the first result, but not if you click I'm Feeling Lucky.)
I get very few "I'm Feeling Lucky" hits, but that might just be because I'm hit #3 for my two best-referring searches.