Given you have a good idea of where to start and are fairly confident you are speaking the same language as your client, jump start research by generating related keyphrases and long tail variants with the ever so easy to use Google Autocomplete. This tool makes predictions based on what you are typing that are a reflection of Google search activity.

This is another common reason people won’t get Long Tail Pro. Their stubbornness can stem from many reasons – including the two mentioned above. Too stubborn to pay for it (can be confused with too cheap to pay). Or too stubborn to learn about the benefits. But the main reason is that lots of people actually think that they are better off without Long Tail Pro. Either they do their keyword research the free (hard) way which takes a LOT of time and knowledge and usually isn’t very effective. Or they use a different keyword research tool which they think is better. Let me just tell you – there is no better or more effective keyword research tool than Long Tail Pro. More than 70,000 marketers can’t be wrong and over the past few years Long Tail Pro has become the standard when it comes to keyword research tools.
It would be great if you can provide comparative analysis of this tool with Google Keyword Planner. Since you’re using this tool so you can provide best comparison. One differentiation which I understood is that this tool works for yahoo and bing as well whereas Google keyword planner works only for Google but Google being a dominating search engine, gives the highest returns, so only this reason may not be enough to buy it.