18-23
Did the traditional college route. (Stanford)
This was great for me because I needed the resources to pursue a gymnastics career. It also exposed me to lots of interesting people and ideas. I had the opportunity to initiate projects and start things. Stuck around for a masters after my undergrad (both in biology) and to use my last year of athletic eligibility.
23
Ran the business operations of my college newspaper.
It was a paid full-time job where I got to manage adult and student staff and report to a board of directors. Great experience running a small business with real revenues and expenses (had to cut expenses massively while reorienting the sales side to stop the revenue decline). Let me know I wanted to be an entrepreneur.
24
Worked in sales and marketing at an ad tech startup. (isocket)
Also great experience - gave me handson skills, saw how a b2b startup launches and starts to get traction. Built my network. Started blogging. Worked my butt off.
25
Started my own startup.
Got together with some good friends who were in startups working as developers. We decided to take the leap and start something. We're targeting a big market and the odds of success are slim but we're hopeful and hungry. =)
Hard to say what I'd do differently. Wish I had done more personal projects and less student groups in college. Wish I had learned how to code. Wish I had started blogging earlier. Wish I had traveled outside the country more (the startup will keep me busy). But since I'm pretty happy with how things have turned out so far, can't really call those strong regrets by any means...
You're asking the right questions - keep thinking about this stuff ... and if you have an inkling of a good idea, DO something abou it, even if it's just to send an email or write a post about it. You never know where it will lead...