I'll share my two cents. I've launched a moderately popular and profitable software product; hardware is probably not an entirely different ballgame.
Try to think a little bit early on about what sort of business you want to run, as that will guide what kind of products you can create and sell, and where to focus your effort individually. Are you just looking for a hobby, to sell a few things for extra pocket money? Or want to develop a small but sustainable lifestyle business? Or maybe you have some capital to invest and want to build something bigger?
Whatever the answer you ought to think at least a little bit about product/market fit. No matter how cool your product is you won't sell much without a viable market of willing buyers. Great product ideas are a dime a dozen but few will find a sustainable market, and since the cost to develop and sell a product is huge a top priority should be finding out quickly and cheaply whether there's a market worth selling to. Otherwise you can end up spending a ton of time and energy and money trying to sell a doomed product to a market that doesn't exist (been there, done that).
I'd go deeper into that aspect but most of what I've learned about testing product/market fit is more suited to software than hardware.
If you're going to go it alone and try to bootstrap a business by yourself you'll probably have to step outside of your comfort zone and pick up some new skills. You've got to be minimally competent at product design, product management, marketing, sales, contract negotiation, accounting, etc... There are a bunch of great books out there that can help you pick up the skills you don't have yet.
The one piece of advice I wish I had back in the beginning would be find a viable market before worrying about building a complete, functional and polished product. I could have saved the better part of a year on my first attempt if I had done that the other way around.