The folks at Groove provide help desk software, so they live right in the midst of the world of customer relationships. So when they publish a list of 10 great examples of onboarding, and each comes with a specific case to illustrate, that's worth reading.
Here is our quick summary, but we suspect that once you scan that you'll want to check out the full post at the Groove blog.
Below is our quick summary version of how to make that critical first customer experience a postive one, starting with this: the critical time is between when they sign up and their first success. (Each specific example that they show is listed below in parentheses.)
They conclude with the strong suggestion that the onboarding process must be evaluated and updated on an ongoing basis: it is never done.