There are a number of ways to optimize your website for conversion—such as by including calls to action and lead capture forms in the right places, providing the information your visitors are seeking, and making navigation easy and intuitive. But the first step is to be attracting the right visitors to your site in the first place. Your goal when it comes to website traffic is to be driving more qualified visitors to your site. That is, those who are most likely to convert into leads and customers.
Use your keyword list to determine how many different pillar pages you should create. Ultimately, the number of topics for which you create pillar pages should coincide with how many different products, offerings, and locations your business has. This will make it much easier for your prospects and customers to find you in search engines no matter what keywords they use.
You mentioned: "many times clients have already done this work. Ask them for copies of their market research reports when you start a project. It will save you a ton of time and effort!" We do this with most of our clients, like you said we have found that around 75% of the have some kind of Market research done, that saves you a lot of time and helps setting up the right SEO Strategy.
Companies that employ overly aggressive techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal reported on a company, Traffic Power, which allegedly used high-risk techniques and failed to disclose those risks to its clients. Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban. Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.