Collect contact information from potential users (e.g. email or phone number). Get them to subscribe to your newsletter to keep them up to date with the progress and launch of your product.

Formspree or Posthog Surveys are some nice tools you can use.

Posthog - Product analytics, Web analytics and Session replay.

Use Web analytics to track the visitors to your landing page, Product analytics to visualize a conversion funnel on your call to action, and Session replay to observe user behavior.

Share your product's landing page on Facebook, post in relevant groups, Reddit or other relevant social sites (optionally you can even use ads to bring google search traffic).

E.g. screenshots of your posts and their permalinks.

Include a brief comparison of each lead channel, highlighting the one that worked best.