Bought the Platinum kit and was able to successfully obtain TN visa at the border (Buffalo NY). The kit… read more provides complete information about the TN process, including things to pay special attention to. You may be able to find bits and pieces elsewhere on the web, but this kit is a credible source with really all the information you need.
The most valuable part of the kit is probably the sample employer letters it provides. I was able to use the sample letter for the Accountant TN category as template, and edit it for my own application by adding in my employer information, job description, and past experience. Having a template is extremely valuable because it saves you time from having to come up the language yourself, and gives you peace of mind knowing that the language and format are proven to work. The letter that I drafted was then reviewed and signed by my employer, without additional edits.