2. The HOW should be something very important to you.

Many experts tell you that you should build something that you actually need yourself. That may be good advise for start-ups but not as good for side projects. Why? Because it's too damn easy to just give up as soon as you hit an obstacle (and you WILL hit obstacles).

But when someone else is depending on your work (and becomes a trusted collaborator), they provide you with that extra UMMPH you will undoubtedly need when the going gets tough. It's a lot harder to bail out when someone is right next to you and depending on you.

But by deciding on your own HOW you will build it, you maintain an outlet for your passion. Believe me, I know. For me the journey of building something is more fun than the anticlimactic using of the finished product.

Works all the way around. Give it a try.