"One of the most difficult tasks for a startup founder is deciding what to do. Where should the tiny number of people working on a brand new company spend their time?  Choosing wisely can place your company on the road to success. Spending too much time on the wrong things can condemn the startup to an early death."

"Choose a key metric to track and focus exclusively on making that metric grow. When deciding what to do, choose the activity that you believe will directly result in increased growth of your chosen metric."

"It is best to pick a metric you are pretty sure you know how to increase.  But it is equally important that that metric matter. And by “matter”, I mean its growth will be a good objective measure of how your company is doing, for example by an investor."

"(b * d) / c b tells you how many of your users, current or new, will be impacted by a new feature, d describes how important that feature will be to the average user, and c gives you how hard it is to build the feature."

"first build the features that affect lots of users as profoundly as possible, and which you can build quickly and cheaply."

"In a company’s earliest days, it is important to place more priority on d in order to ensure that you have product/market fit. It is useless to try to grow or scale before finding 100 users who really love your product.  Only then should you refocus on b and grow your user base in order to get the data you need (from your customers) to determine where to build depth."