When I'm emailed a spreadsheet or sit through meetings where I'm talked at, I know it's going to be a bumpy ride. More often than not, an onboarding process is born, but never enhanced. Usually v1 is good enough, but good enough isn't good enough. Your customers are evolving so your OX (onboarding experience) should too.
My secret to designing enjoyable onboarding experiences is putting myself through the onboarding experience every six months. I do my best to put myself in my customer's shoes to see what the experience is like. In order to be really objective, I ask myself: "Is this onboarding a chore?"
The perfect OX is out there. It will take time and lots of iterations to get there, though. Here's to not giving up! 
What secrets do you have up your sleeve to design a solid OX?