Never, count solely on your family and friends for feedback and help. Family and friends can offen by either to charitable or too destructive with feedback.
Know how much money and time you can devote to the startup. Keep a watchful on your money
Other may disagree with this but I believe it with every fiber of my being. Build your tech only toward useful customer features. Without a product to sell/service to subscribe to there is no tomorrow for startups. I'm not saying tech debt is not a real thing but I worked for startups that maintained a very low tech debt while amassing a high money debt which lead to closure.
Begin promoting as soon as you have something that sort of works.
Just a few quick thoughts
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.