1. I would read all the books and articles I have written on business, but then of course, I hadn't written them, because I needed to have had experience before writing them, so I couldn't read anything I hadn't written yet. Read every book and every article on business!
2. I would not have wasted a year in rented property, but would have bought a place right from the beginning. Never rent, if at all possible!
3. I should have avoided customers who don't pay on time and customers who are more hassle than they are worth. Learn to fire the bad customer!
4. I should have fired those employees who didn't deliver on time the first time, instead of listening to excuses, in the vainglorious hope that they will improve. Idiots and lazy work-shy fools never improve, so drop them asap!
5. I would have borrowed less and saved more. The grandchildren of capital get 5% and that makes them over 300-times richer than the grandchildren of those that live on credit. Read this lot - and learn that it's all about percentages -
http://www.ukbusinessforums.co.uk/articles/r-g-but-only-if-they-dont-take-it-from-you.657/
6. Just do it! Don't talk about it - do it! You want to become a movie director? Spend a few years learning about directing and the movie business, then pick up a camera and make a movie! You want to start a car franchise? Work in the business for a while, then buy a plot of land and start selling cars! You want to start a radio station, a magazine, a restaurant, an hotel, write books? Life's short! Blink and you'll have missed it! Learn the ropes and then do it!