Make something. Most people won't want it. Show it to lots of people until you find some who are mildly interested. If nobody's interested, make something else. Otherwise, make what the people who are somewhat interested want. Repeat until you've made something people want.
Want something. Find other people who want it. Research the hell out of possible ways that you might make it. Talk to lots of people that might help you. Most won't, but some may give you some pointers or point you toward people who can help. Repeat until you've made something people want.
Empirically, the second seems to converge faster, but both can work. People tend to fall on different sides of the "I make things" vs. "I want things" spectrum, so the first approach will work better for some folks and the latter better for others. (I'm very much on the "make things" side of the spectrum, for example, so was basically forced into starting by making bad ideas and then incrementally refining and retargeting them until they become good ideas.) Know your strengths and what you care about and play to that.
Also, it can help a lot if a "make something" person partners up with a "want something" person, but this requires that they have compatible interests, working styles, and personalities. This itself is kinda a magic combination...if you find a team that works, run with it, but if you don't, either keep making things or wanting things until you do.