I'd suggest you go read The Lean Startup, as this is the source for the suggestions on HN.
You validate ideas by applying validated learning:
1. Figure out what you want to learn (ex. an assumption: customers want this product because it allows them to easily do x)
2. Figure out how you will learn via metrics (ex. measure: how many customers sign up based on advertising based on this assumption)
3. Do what is required to gather the metrics. (ex. act: advertise based on the assumption to gather metrics for analyses to validate your assumption).
Sort of sounds like Act/Track/Learn :)
The Lean Startup proposes that you approach a product by asking the following questions:
1. Is this product valuable to my customers?
2. Would customers buy this product?
3. Would customers buy this product from me?
4. Can I build this product?
Point 1 & 2 refer to validating the viability of ideas, while 3 & 4 is more of an introspection regarding availability of skills/resources/advantage etc.
Good luck!