How did you make sure your product launch was going to be successful?

Hi there! I'm building a product and recently here on PH I've seen a post that was talking about steps before launch and that person sent a link outlying them https://docs.google.com/spreadsheets/d/1-ZPKqYV9pj79s67Nw7jiCqnA7W3bwM0TGWhsvc3J09w/edit?usp=sharing can't remember what post it was. What did you do to make sure the product had a successful launch? Also, if you've launched other products, what things you've done that were poor decisions and why?