What is the best way you know to validate an idea?
This depends a lot on what you mean by 'validate an idea'.
If you mean - validate it's a potential business: put a price tag on it.
If you mean - validate people will pay attention: put a signup page somewhere and work to drive traffic to it.
If you mean - validate the tech will work: build the smallest/cheapest MVP you can.
If you mean - validate that you should spend time on it: determine which of the above *actually* interests you (and who you can get involved that would be interested in the other bits).
Ultimately - almost all ideas will eventually work.
The question is more about are *you* in the unique position to be the one that makes it so? Are *you* really ready/willing to push that boulder up the mountain?
How long do *you* expect it to take you? How realistic are *you* being about the timing, the market, your unique advantages, your commitment?
Validation -- especially in the very early days -- should be as much if not more about internal and self-realization as it is any external perception.