Keyword Research is probably the first thing to do. You might enven want to do it before naming your product or finding a domain name. Why?
Because it might be very important to find out what words people are using to find out about you and your products and services:
Let's take a real-life example from one of my clients:
I periodically research every search containing hawaii, hawaiian, plus the name of each island. Imagine how happy I was to discover that about 300 people a day were searching for "hawaiian arm tattoos" but only 2 sites were responding. So I wrote and article and put it on the Hawaiian Travel News site, thus drawing about 9,000 hits per month as a result of getting the 3rd position on google.
Keyword research can also tell you how many people are interested in your product. It is possible to discover exactly how many searches were performed last month for terms related to your product or service. You could save a lot of money if you discovered people weren't interested, or make a lot if you discovered they were.