Essential tip #1. No customer cares what you do, only what they get. They're not buying the reverse engineering, they're buying the copy. Let that inform your choices, your marketing and interactions with the customer.
Tip for B2B especially. Listen to the person and treat them as a professional, find ways to explain limitations and options in a way that makes them feel understood and that helps them look good in their own organisation. In another phrasing: Make them the Hero of their company, and you'll be theirs.
Word of advice: Enjoy the ride! Business isn't difficult, but it's tough, there's so very very very many things you now have to get done there's no reasonable chance at foreseeing even most of them. You will get surprises, you will get crises. Get as much help and mentorship from experienced entrepreneurs as you can (we're typically a very helpful bunch), but prepare for even that not being enough.
Perseverance, responsiveness, and resourcefulness is what separates you from the 80% failed businesses within 5 years.
Depends on what you do; if you specialise, there aren't other places to go to, if you're easier to work with, deliver superior quality, are more responsive or just plain likeable, people/customers will stay with you for longer.