How do you start a tech startup as a non-technical person?
You can't just "start a tech startup" because nothing happens by itself. You need funding, and you need to have some experience running such companies. However, if you convince someone to invest in your idea they will expect that you know something about managing a team of people and that the idea is solid enough for someone else to start working on it with you (which is actually not very hard).
What do I mean by technical or non-technical? A good way of describing it would be: are you comfortable dealing with people who are smarter than you? That's how I see myself — when there is an issue that's hard to solve, I just hire someone smarter than me to solve it.
So what do you do if you are not technical? You identify your strengths and weaknesses:
Are you able to lead people who are smarter than yourself? Personally, when there is an issue that's hard to solve, I just hire someone who is better than myself at solving the problem (which has never happened yet). It sounds obvious but actually most founders don't fall into this category. If you can't rally people around a common goal - stop right here, because that means that no matter how great your idea is, it will have zero chance of succeeding (unless you find a co-founder/investor with charisma).
Do you have a technical co-founder or are you planning on finding one? If yes - what's your plan for working together, how will you make decisions etc. If no - can you afford to hire people who are smarter than yourself and how will you find them? (I wrote a separate post about hiring tech talent)
What kind of experience do you have running companies? Do you know when to say "No" to customers? Have you worked with investors before in some capacity? Do the founders feel like peers or bosses? How many times did the company fail before it succeeded (if ever). Experience is everything. You might not need any relevant expertise (in which case engineering knowledge would be a plus), but you at least need experience running companies.
What can you offer? A different perspective or domain knowledge is usually very useful, so I wouldn't underestimate this strength of yours. Just because you are not a programmer doesn't mean that your input isn't valuable!
How much do you want it? A lot, right? And you are aware of the fact that there will be moments when no one around believes in your vision (including co-founders)? Are you ok with spending every waking moment on making sure the company succeeds? Because otherwise, maybe it's better if someone else tries to make it happen — otherwise more people will lose their time and money than need to.
But what about already being a programmer? If you're a programmer yourself and this is your primary strength - you are in the best position. You can just skip steps 1-3 and go straight to building something.
So, putting it all together - if there was one thing I'd advise for non-technical founders who want to get into tech startups: hire someone who's smarter than you (even if he's not an experienced founder) and make sure that person has appropriate decision making privileges, because most of what will happen next will depend on his decisions — whether it's hiring people, negotiating with investors or other crucial business relationships.
For technical people reading this post, my advice would be similar - don't understimate domain expertise! Treat this person as a partner and you might get something big out of it.