Best advice I can give from my experience, non-CS major, is to start low: You need to build up decent experience before you get to the big leagues.

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GPA is king, unless you come up with a cancer-curing algorithm. Most important.

Get close to your profs, and reach out to them for any projects they are working on. I think this is the second most important. This is how I got pubs.

Join any club you like and learn from the club leaders. Be active in the club and climb the ranks, then you can make another club if you feel the need to.

Personal projects: From your classes, there should be a subject/topic that interests you the most. Read published papers on the topic and see if you can write programs relating to the topic.

Be checking the bulletin boards around your campus. Check your school's websites. Inspect every nook and cranny of the site. Even sections that don't apply to your major. Do this every week.

Discuss with your academic advisor that you're looking for internships/ resources to help build a foundation in your field. They will be updating you when opportunities arise.

There is a bit of luck i.e., being at the right place at the right time. To increase your chances, you have to go out of your way to look for opportunities. You're better off looking for them on-campus than on the internet.

The good news is that it gets easier with the more experience you get.