The Validation Method
One of my favorite books is Lean Startup. In there he talks about "validated learning".
So what you do is you create a minimal viable product (or MVP for short). This is like the most basic product you possibly can do.
You give it to a few people, get their feedback ...and use that to tweak it so it's more "right" for your market.
Now this process is super important because if you start off with the wrong product in the very beginning, it's an uphill battle and it's ALWAYS going to be tough.
(Trust me on this one.)
Anyway - the whole point of doing this is to quickly figure out if you're on the right track with your idea or not.
And the best way to do that is by creating an MVP and giving it to some of your target market and asking for their feedback.
I know this sounds really simple but it's amazing how many times people try to just build stuff without testing first.
Don't do that!
It never works out well lol.
Anyway - once you've created your MVP and tested it out, now you can start building out your real product.
But before you do that, make sure you take notes on everything that worked well and everything that didn't work well.
This will help you when you build out the final version.
(See - even though we're talking about digital products here, this still applies to traditional businesses as well. Everything I talk about works for both types of businesses.)