My first step is to put the idea to the side, grab a piece of paper and write down a couple paragraphs explaining the problem. Then hide that piece of paper, wait a couple hours, and write down the problem again, and hide that piece of paper.
Once I feel I have gotten to the core of the problem, I make a list of 10 people I know who I think have the same problem.
Then, I find some time to meetup with them, or hop on a call and tell them about the problem. Then I shut the hell up, and just listen to how *they* describe the problem and how they deal with it.
Hopefully, by the time that is done, I have learned that there is already a solution I didn't know about so I don't have to waste a year or two of my life working on an idea.
1) Decide what statement you need to prove to validate your business and then figure out how cheap you can validate that for, even by faking it.
For example, Skillshare validated the statement "people will pay for classes taught by their peers" with $10 and a Wordpress site hooked up to Eventbrite checkout. That validation proved the core of their business and removed a lot of the risk of the next steps.
Validate it by talking to the industry that it is for right away.
You need to see if it is a pain or just a cool idea.
You should also start selling it even if you don't have the product. (Is it painful enough for them to take out there wallets? You need that kind of idea.)
Who is your market? Where are there? How do you get in touch with them?
Is it a big pain (you idea)?
Will they buy it?
Try getting them to buy, then go create it.
I could talk a ton on this, but go to my profile and watch the video. It will give you a good idea of a process to follow to presell and validate your idea.