* Only solve a problem you have experienced - this makes ideation and validation much easier (though its still essential to get unbiased opinions on your MVP)
* You'll need something to attract people initially to get feedback and validate - but don't dedicate more than 2-3 weeks of coding to your beta.
* Product Hunt allow you to post twice - once for beta and then for V1. Your initial PH post should give you more than enough test users to get good feedback. Don't bother with any other marketing or coding until you have a validated product.
* When it comes to feedback, schedule beta testers in for calls before giving them access to the product; always opt for calls over email
* Technology doesn't matter, as others have said your selling a solution, not code. Opt for whatever language or framework you will be fastest to build in.
* Once you have a validated product you're ready to sell, feel free to experiment with different marketing channels but quickly determine what the most effective for your product are (in terms of volume of leads and ROI); dump the rest and double down on these. The internet of awash with cool marketing tricks but the reality is that most companies get 80% of their leads from 1 or 2 refined, targeted actions.