Bad data gives us false negatives (thinking the idea is dead when it's not) and—more dangerously—false positives (convincing yourself you're right when you're not).
Immerse yourself — A+
By immersing myself in the community I met a load of people and soon had all the connections and conversations I could handle.
Pick a target audience — A
Before we can serve everyone, we have to serve someone. Forgetting about all the possibilities and focusing on who would most likely buy.
Listen more than you talk — A+
1. Talk about their life instead of your idea
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3. Talk less and listen more
Ask concrete questions about their past — A-
"Talk me through the last time that happened."
Good question. Your high school writing teacher may have told you that stories are meant to "show, not tell". Whenever possible, you want to be shown, not told, by your customers.
Stay away from hypotheticals — C
"Would you pay X for a product which did Y?"
Bad question. The fact that you've added a number doesn't help. This is bad for the same reasons as the others: people are overly optimistic about what they would do and want to make you happy. Plus, it's about your idea instead of their life.
Look before you zoom — B+
Everyone has problems they know about, but don't actually care enough about to fix. And if you zoom in too quickly and lead them to that semi-problem, they'll happily drown you in all the unimportant details. Zooming in too quickly on a super-specific problem before you understand the rest of the customers life can irreparably confuse your learnings.