1. contribute to a significant open source project
2. write some significant work of software
3. design and build your own computer
4. build a robot something
5. work as an intern in industry
6. do work as a research assistant
When I was at Caltech, students did (entirely on their own):
1. built a gas powered helicopter from scratch
2. built a tracked robot with an arm and a manipulator
3. built an electronic synthesizer
4. built a functioning railroad that ran through the dorm
5. many built a single board computer for their own use
6. designed and built the campus radio station
7. one fellow designed, built, and sold custom speakers in the student workshop. After graduating, he turned it into a real business and made a fortune
and so on. In other words, turn yourself into someone useful to a company.
BTW, Caltech places emphasis on get-up-and-go in their student selections. I was a marginal candidate, and I found out years later that my projects I worked on in my spare time made the difference. I was always building things in the garage and in the high school shop. (But I didn't tell them about the flame thrower I made from a lawnmower.)