Reading specific books ('Think and Grow Rich', 'The 4-Hour Workweek', 'On Rental Property Investing', 'How to Win Friends and Influence People', 'Rich Dad Poor Dad', 'The Millionaire Fastlane', 'Die With Zero', 'Your Money or Your Life') over a year will significantly increase business acumen, practically guaranteeing increased earnings.
"if you actually go and buy these books and then actually go and read them over the course of a year I guarantee you'll have more business Acumen than 99.9999 of people on the planet and because of that it's practically guaranteed that you will make more money as a result"