Threaten to tattoo "We are not the user" on the inside of your team's eyelids.
Smart people often end up building for in a way that makes sense to them because -- well -- they're smart people. Your core user may have a different level of sophistication, different goals, and even a different background using technology.
Watch your customers use your software and focus on decreasing the time it takes for them to get the value they're looking for.
Interact, don’t tell in your onboarding process.
Make it easy for new users to experience your value proposition by providing actionable, responsive guidance and removing passive, obstructive content like popups, videos, or slideshows.
Don't just provide linear, step-by-step product tours but instead provide guidance in response to the user's path through the product.
Seeds of churn are planted early. If your sales process or your onboarding are broken, you'll strongly limit the growth of your company and you'll loose on the long run. Make sure your funnel isn't leaking.
On that last point: Startups don't have much ressources. Prioritizing work is primary to your success. Always ask yourself "What's our biggest constraint right now?".
Experiment on that area and measure your results. As soon as you lifted the constraint, move onto the next one. That process will allow you to create a repeatable, scalable and predictable company you'll be proud of.
To keep your optimization processes simple prioritize your actions by effort and impact.
By keeping your test size small, you’ll learn faster and validate whether it makes sense to continue to invest in an approach.