How do you validate your product idea?

Try to get traction before launch, via sign-ups or waitlist. Share your idea on forums to see if there is some interests. The reality is though, you won't be able to truly validate until you launch, Consumers don't know what they want until you show them, and your ability to execute plays a hand in whether your idea is valid or not 😃

I would start with defining the target group. Talk to them, ask for their problems and try to find valuable solutions.

Sell the thing before buidling anything. I have a side hustle that frames online newspaper articles for individuals. Before building a website or even having stock, I sent 50 cold emails to people appearing in eg TechCrunch. 25% wanted to know the price. If it's an app, create UI / mockups and try to book demos with potential clients. ps I have a sales background but marketers would probably create a landing page, run some ads and measure the interest based on the number of people on the waiting list.

We are making an MVP to do it. As for me, it's the most reliable way.

Launch your MVP on product hunt as soon as possible. :) You can relaunch after 6 months if you have some feature updates. All upvoters of your first launch become followers of your product hub page, so you can build up an audience over time.