To win big in online Hold'em poker, focus on mastering the fundamentals, such as hand selection and position. Play tight but aggressive, capitalizing on strong hands while avoiding unnecessary risks. Pay attention to your opponents' tendencies and adjust your strategy accordingly. Utilize bankroll management to ensure longevity in the game, and take advantage of online tools and resources for analysis. Lastly, maintain a disciplined mindset, avoiding tilt and emotional decisions, to consistently make the best choices at the table. With practice and patience, you can significantly increase your chances of success.