Crafting good hypotheses for your startup is hard. Most people focus on solutions rather than problems. That leads to a ton of products getting launched with zero traction; the all-to-common "solutions looking for problems." A good hypothesis is important because it leads to good experimental design. Good experimental design is important because you need it to properly validate or invalidate what you're doing.

There are two main assumptions that every startup inherently makes, what Eric Ries calls the "leap-of-faith assumptions". These are the value hypothesis (will users find value in this product?) and the growth hypothesis (growth rate of users). The growth hypothesis comes later, but first you need to prove your value hypothesis. Come up with a clear, short, succinct product description - and then continue to refine it with additional comments.

Here are some examples of core value hypotheses:

[For a New Restaurant Guide]: People do not try new restaurants because a) discovering new restaurants is too hard; and b) they are worried about being disappointed

[For a new taxi service (Uber)]: A lot of people will pay a premium for rides if they receive prompt pickup and can ride in a luxury car.

[For a social media suite (Hootsuite)]: Large brands and individuals will pay a monthly fee to consolidate their social properties, have better filters for 'what matters' on their social stream, and better manage their communication across social services.

Note that all the examples above make a hypothesis about what people will value - it's not a description of how you'll fix it.