First you identify who your target audience is, your client might know some about this but it's important to also talk to other related people. So you start to talk to commuters, but also moms who bring their kids to school, traffic cops, people at highway stops, anyone. At the beginning you talk about their experiences, what do they do and why?
Then you want to formulate insights from these interviews and what you have learned from research, for example: Commuters get annoyed by loud noises and honking while standing in a traffic jam.
Then you could ask people who you talked to previously to come in and help design something. (this is also a good moment to ask more questions of you have those) Do a session about people drawing their experiences on a white board and brainstorming together with you and other participants in how this might be solved.
Then you build a MVP and test this with your commuters
Then you improve and iterate and test this again.
If the vibes are good you continue to develop your product.
(this is in short how it works, if you'd like to learn more and get specific tools and techniques tech out this: http://www.designkit.org)
You can actually watch this process in action on Steam's Early Access, a platform for selling games during development. Mobile app stores also provide that feedback loop where your users are able to share their frustration or happiness each time you update and may even segregate feedback by version for you.
Don't confuse the smallest version of your app for a pre-registration launching-maybe page either, that's the smallest version of a dream about building a startup.
You have to look for unrecognized unsolved problems. It's the "unrecognized" that is the bitch in this problem. "Unrecognized" might just be the core feature of entrepreneurship. You have to work hard to uncover it. No easy answers.
I suppose there are established techniques in market research that would help. Ask someone who is good at market research.
To build something people want the first real step is collect your first users. Then after it's everything people mentioned here...
A good approach for good ideas is to find a niche with a problem that can be solved with current state of technology but they are not aware of. Good old automation.
MVP advocates putting your product out there at such an early stage to find out if it's actually a terrible idea before you commit to the entire upfront cost of building the complete product. The iteration enables your users and customers to influence product decisions as they arise. These can be positive additions to a project, or just as importantly signal it's a bad idea that isn't worth pursuing further.
Learning and getting good at user research takes time and money, mistakes will be made. Don't forget your competitors are doing their own user research and iterating too...In my opinion, many startups die right here because of founder optimism bias on these exact "soft skills" questions you asked about. Founders, who are smart, skilled at many things and fast learners, still regularly underestimate time and cost to get good and be better than their competitors at this stuff (assuming the founders remember they have competitors).
It's sad but many startups run out of money here still learning to tie their shoes - they never even enter the real race of running a business (though they won't admit this usually). Anyway, if you still want to learn how to "listen to users" and "make products users love" a full explanation is beyond the scope of HN, but here is some basic info/an analogy how it works:
Guy: Hi, sorry to bother you miss, but will you marry me?
Girl: Um, What? Who are you? Why are you bothering me? I don't know you and anyways I have a boyfriend already. Bye.
Guy: Wait, please. How long have you been with this boyfriend? Is he perfect for you? Marriage material? Because I can be perfect you.
Girl: Haha. No, he is not perfect. Far from it. I like him but don't love him. Communication kinda sucks from him, he ignores my texts or just takes way too long to reply to me. Like over 10 minutes before I get a reply. We have other problems too, typical shit couples deal with. Wait, who are you again?
Guy: Sorry. Hold on. Writing down everything you said. Communication...Not fast or reliable...Please tell me more of your problems. I want to marry you. I am very passionate about marriage. I really want to eat, sleep and serve you. Help me, help you?
Girl: You're funny. But sorry, you are not my type physically. I have to be attracted to person I am with. Also I want to marry a guy I love, Someone who is my best friend... I want someone who understands me, anticipates my needs before I even know I have them, someone who texts me back in less than 10 minutes. I want someone old fashioned. So like you should pay for everything at least at first. Really I want someone who is 10x better than anyone else, including my current boyfriend, if you can't offer that don't bother proposing again.
Guy: Got it. I can do plastic surgery. Consider it done. Also, I wrote down the list of things you said you want in a husband. And I made a note with all the problems you mentioned you were experiencing and hated. I left space in case you think of anything else. Can you give me a few weeks to work on myself, looks and personality and other qualities, before we meet so I can propose again?
Girl: Wow I have never seen someone want to put in so much effort for me. Guys are so selfish usually. Someone who put me first...if true I think I could see getting serious and loyal to someone like that, maybe even love. But can we meet in 2 weeks instead of a few weeks? If you are making changes for me I want to make sure you are on the right track with small changes instead of waiting to meet only after big changes, no? I mean you don't even know me.
Guy: Good point. I was thinking about that. I actually want to know much more about you. More than just knowing your thoughts on relationships and marriage, I feel like the more I know about other aspects of you the better I can understand you and make changes I know you want. Any chance I can learn and know literally everything about you? including your private conversations with your friends?
Girl: Ya I don't mind if you know everything about me including my most private info. Here is my Facebook info to start. Really looking forward to you selling me this marriage and anything else :)
The End. Repeat for 10+ years.
I like benologist's reply, as well.