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.
Spencer, it seems like you got out at just the right time and made your money? Seeing as Google has basically stopped giving access to their free keyword tool. I own the FULL lifetime license $290+ I think is was. Now Longtail Pro is useless due to the restrictions that Google has put in place. Do you know what the future plans are for Longtail Pro to get around this issue that I’m sure everyone is facing? Or can you get some feedback from the new owners?
1) SEMrush - I believe that among all the 3rd party software, SEMrush has the largest keyword database. Their search volume data is pretty accurate and aligns with the Google keyword planner. Also, based on the type of content that needs to be produced (i.e. informational, transactional, etc.), one can utilize different filtering options available in it.
In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input. In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).