How do I improve my judgement – technically and in business?

I have found that generally the longer I delay a decision, without abandoning it, the better I understand it, and that lets me make better decisions. Snap decisions are highly unreliable. I have made some awfully scary snap decisions. I don't want to do stupid things like that again.

Keep a journal.

1. Make a judgement

2. Write that judgement down and the activities guiding the judgement. Say what you thought would happen and why. Include the context, a clear problem statement, alternatives and possible outcomes, consequences, and expected outcome.

3. Review the entry when the outcome of the judgement is clear. Note any discrepancies between the judgements and the outcomes.

4. Every six months or so, review the entire journal.

You could look into the OODA loop methodology.