Write your onboarding steps down before you automate them
It's tempting to jump straight into building automated messages and reminders without first writing down what your onboarding process actually is. That's a mistake. I've made this mistake myself, building automation around whatever I happened to remember that day instead of the full process. You can't automate a process clearly if you can't describe it clearly to yourself first.
Sit down and write out every step, in order, from the moment someone signs on to the moment they're fully set up and working with you. Include who does what and roughly when it happens. This document becomes the blueprint for anything you automate later, and it also works as training material if you ever hand part of this off to someone else.
Skipping this step usually means building automation around whatever you happen to remember that day, which leaves gaps you won't notice until a client falls through one of them.
Try this today: write out your full onboarding process on one page before adding or changing any automated step.