General Questions regarding preflop play / leaks

[mimicme]

1. In live full ring games, suppose the table is pretty decent, not everyone is a rock, how often should you be cold-calling 2 bets. Should you always take a 3 bet or fold mentality? What situations would be good to cold call 2 bets? How big a leak is it in a tight game?

2. What are mistakes players generally make that are huge leaks?

3. What are mistakes players generally make that are minor?

4. How important is getting extra bets in and value betting thin? Or what are situations where players aren't maximizing their winrate?