My personal approach is have the idea, maybe I’ll spend a day or few brainstorming (paper and pen), I sketch out the solution. I have a shorthand for this, I usually just sketch out the data model and I can visualize the front end functionality. I don’t need to do mock ups or wire frames. That’s a time suck. If I feel good that, this could be cool (useful, problem solving, easy to communicate, etc)...
I run through every user acquisition channel and think of a strategy. Think of tactical execution. What’s the likelihood _I_ could execute with success. The I in the last sentence is key. I see plenty of people executing big ideas I had, but could never had executed. Know your abilities. Do I need help? Do I want to hire(invest)? Do I want to spend money on ads?
I personally avoid anything free. I have noticed, if I expect something for free, it won’t come. For example, if you think about making something viral or network effect. Certainly build that in, and leverage it. But don’t hinge your success in it. It’s probably a multiplier and you need to build the base.
Once I get to the part about investing my money. I’m a pretty frugal person and don’t like wasting money growing hobby sites. So this is a good filter for me. It also helps me think of what does the product need to look like (mvp or further) before I feel like dumping resources into growth. Using this I can estimate how much work I have ahead of me. I only have 10-20 tinker time hours a week. So again do I need help? Am I going to dedicate weeks to an alpha/beta?
This type of thought process easily exposes most ideas to be things I just simply don’t want to do for some reason or another. This is just a simplified description of my personal way. I have a lot of biases like not wanting to seek VC funding, or really even have to build a team.