My name is Samuel Hulick. I'm the author of The Elements of User Onboarding and run the website UserOnboard.com, where I review the first-run experience of many popular web apps. If you have questions about user onboarding, UX in general, or my experiences in particular, I'm an open book. You might be surprised what I will answer.
Moderator's note: I highly recommend you check out Samuel's onboarding teardowns. They show you how popular apps and websites onboard new users. The teardowns are both insightful and a joy to read due to Samuel's witty humor. Samuel has also published a book that goes into more detail how you you can optimize the onboarding process of your product. Lastly, he publishes articles on his Medium.com collection called Designing for Results.