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. 
Calculating the CTR of two different ads is easy – predicting how they’ll perform over the long term is much harder without running a lengthy A/B test. Perry Marshall's SplitTester tool allows you to enter numerical CTR data to predict the ongoing performance of the two ads. Great for estimating statistical significance if you don’t have enough time for a full A/B test.
Similar to Google Suggest – but with a lot more data – Soovle lets you see autocomplete suggestions instantly from not just Google, but several other sites including Wikipedia, Amazon, and YouTube. Very handy, but it’s worth noting that Google plans to cut off access to the autocomplete API in the near future, meaning Soovle will only be able to provide results for other search engines when this happens.
Once you are happily ranking on Search Engines, you will need to discuss with the experts at your SEO consultancy whether you should expand your keyword portfolio and target more keywords or choose to maintain the optimization of your site. This will depend again on factors such as how many pages your website has, the competition in your industry, the traffic driven to your site, your conversion rate and so on.
The All in One SEO Pack plugin has more than one million active installs. You won’t have to look far to find competitors, but there’s a reason why so many people use this tool. Not only is it free and simple, but it’s results can’t be denied. It will definitely help your website, from an SEO perspective, which is something all new businesses are interested in.
Typically, the number of keywords targeted depends on the size and scope of the SEO project. Once an SEO strategy plan has been mapped out, the analyst will have a better idea of the number of keywords, a plan can be developed for how those keywords fit in with optimized pages and link submissions necessary to make progress in the SERPs. Analysts start by researching keywords and coming up with a shortlist both the agency and client are happy with. This may include several research methods including keyword recommendations from the client, customers and suppliers, surveys, using keyword research tools and so forth.
If you havent see it already, check out the links in shor's comment below - there are some great resources in there. In some cases you can also consider surveying your current audience or customers through email, on-site surveys or SurveyMonkey.  Be sure to ask for some profiling information that you can use for determining specific persona needs like age, sex, location, etc. (Probably best not to make it sound like a creepy text chat like I just did though...)  :)
Like many SEOs, I was hired with one vague responsibility: to set up an SEO program and achieve results. Like many SEOs, we jumped right in and started spewing out SEO audits, rewriting title tags, offering up backlink suggestions, rewriting URLs and so on. And like many SEOs we promised results. But what we didn’t do, until that fateful launch, was develop a comprehensive strategy.
Like many SEOs, I was hired with one vague responsibility: to set up an SEO program and achieve results. Like many SEOs, we jumped right in and started spewing out SEO audits, rewriting title tags, offering up backlink suggestions, rewriting URLs and so on. And like many SEOs we promised results. But what we didn’t do, until that fateful launch, was develop a comprehensive strategy.
We now have a dedicated SEO strategist who, among other things, develops 90 day plans for our websites. 90 days isn't longterm planning, but at least we have a strategic objective for the quarter. He also works closely with our UX team to identify the target audience - the crew that does the persona research and focus groups prior to the wireframe stage.

This is excellent and should be intuitive for marketers (and SEO pros are marketers!) but we often take the short cut and neglect critical details. What would also reinforce the strategy is way of providing solid projections for SEO (these could be based on industry trends and statistics). Clients now ask for ways to calculate ROI and they need numbers to get budget approvals. Increase in traffic by X,  increase in qualified traffic and leads, conversions etc, some way of quatifying the expected return.
The first step of an SEO strategy is to complete a through analysis of the website and its competition. During an analysis (or when it is a top-to-bottom analysis with a reporting component, an SEO audit) the consultant can see firsthand the strengths and weaknesses of the current technical infrastructure of the site, what keywords have been targeted previously, the on-page content, the link building profile and competitor analysis. It is essential that clients are straightforward with optimization experts about techniques they have used in the past.
Thanks for bringing up this point - I agree Eric - competitive positioning can help you determine value that you bring to the table that your competitors dont.  I'm all for it.  Neilsen does some reports that provide awareness, likelihood to recommend, sentiment and other insightsfor your site/brand and your competitors. You can also pull some of that type of insight out of social listening platforms like NetBase, SM2, Radian6, Dow Jones, Nielsen, and so many others.  I've even done some hacked compeitove sentiment comprisons before using Search: searching for [brand or feature] + "like", "love", hate", "wish" etc. 
Enter in a URL and this free SEO tool will tell you the keyword density of all of the phrases on the page. Find out how strong of a keyword message your content is sending with the Keyword Density Analysis Tool: Get hard numbers on your content ratios to find out if you need more or have too much. Use this tool to ensure a solid balance of keywords within your content and to match the right keywords to the right pages.
One of the biggest challenges in lead generation campaigns is learning enough about your leads to qualify them. Convertable makes this easier, offering much more data than traditional forms allow, providing you with data on everything from the browser they used and their operating system to the traffic source and the keywords they entered, as you can see in the screenshot below:
Why not? When you skimp on tools, you hinder your marketing from getting better. So, regardless of whether you choose these specific tools or not, make it your goal to find tools that you use regularly. Better tools are equivalent to better marketing. Whatever the tool you choose, make sure that you understand it well and that it makes a measurable improvement on your marketing efforts.
I second Rand's comment!  Congrats on moving from the corporate world to the independent consultant.  This is my goal for the near future.  I too have been testing the waters of independent consulting, but it doesn't quite pay the bills yet!  Sometimes I feel like I should find a mentor who has been where I am now and is where I want to go.  Perhaps i'll find a few in this community over time!
As I had a teacher at school who was always really picky on how to draw conclusions I must say that the conclusions you drew for your health situation might be true, but dangerous. For example: If slightly more women than men suffer from health deseases it could be wise to write the information toward women. But, if you take search behaviour into account thing could look a lot different: It might turn up that men search more than women or that (senior) men are more present on the net than women. 
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