How do you normally validate ideas quickly?

I have a few ideas for startups and i release I sometimes want to throw up a quick wait list to validate my idea I'm considering creating a product that uses AI to generate the style of a wait list for you and host it on a subdomain of SaaS product all wait lists will receive email addresses and you can see analytics. it's something I think I would want for myself but you tell me is that something you would be interested in? and how else do you normally start validating your ideas?