If you mean "How can I buy stock at $25 and sell it right away to the general public for $35 to $50 on the same day?" Then the answer is, "Sorry, you can't."
If you mean "How can I create a company that will allow me to sell a future interest in the company for way more than I put into it?" Well that answer is "Play the tech startup game."
During the Dot-Com bubble a company often had a 'friends and family' plan where if you had a family member working there or knew someone you could participate in some small way in the IPO. I know families that no longer talk to each other (even now over a decade later) because of that 'opportunity' so I'd approach it with caution if offered.
