What you need is a product or service that you can sell. So, probably the first thing you need to do is identify a need with a market. This could be anything from Paypal enabling financial transactions and taking a cut on each transaction to mommy bloggers selling ad space on their blogs.

The right time is now. It doesn't matter where you are at or what you are doing. If you identify a need and you are ready to put in the resources (time and money) to deliver on that need, then act on that. You may not be in a position where you can scale up with staff and funding like a Groupon, but there is probably a lot you could do on your own. At least you could get your ideas to "minimum viable" so that you could dip your toes in your target market and get some feedback.

I think that you will find that the best way to start answering questions is to simply get started. You will make mistakes along the way and you will learn from those mistakes. You will gather information which will allow you to makes changes based on that feedback.

Otherwise, every business opp brings different circumstances. Just do something... NOW!

Finish your degree then work for the largest, richest, most prestigious organization that will hire you. This will expose you to successful people, show you how businesses work, give you credibility, and introduce you to more opportunities.

Build something cool.

Try to get people to give you money for it.

Evaluate the results.

Repeat as necessary.