Start with a hypothesis, and other good design advice

A few months ago I came across this post by Avinash Kaushik which lays out three excellent design principles (paraphrased slightly):

• First get over your own opinions
• Start with a hypothesis ("In every well crafted hypothesis is a clear success measurement... If you don’t see a success measurement in the hypothesis then you don’t have a well thought out hypothesis.")
• Create goals/decisions before hand

You can tell from reading the post (about creating a testing/experimentation program) that Avinash is an analytics guy. But I think these principles generalize to many design problems; regardless of the situation, "start with a hypothesis" strikes me as a solid piece of advice.