What are the best frameworks you've found for validating startup ideas?

Talk to 10 Framework

Step 1. Talk to 10 potential customers. If you can't make a list of 10 potential customers your idea is not specific enough. If you can't reach 10 potential customers (like busy doctors) you customers are not reachable.

Step 2. DON'T ask them if the idea is good. People want to be helpful. Ask them what they are ALREADY doing to solve the pain you plan to target.

Repeat until you stop learning new things. You should have a pretty good idea of what to build or sell.