Factors contributing to Research apart from publishing Technical Papers
A senior thesis (or, if you're engineering, your senior project, if you did one) would probably be a good thing to showcase, as it demonstrates both your ability to perform work in a group as well as your ability to write.
Internships are great. They show that you can work and it also can serve as a reference.


If you've done anything else particularly notable (e.g., won a nationally recognized science fair), you can mention it, but the number of people who've done stuff like this is pretty miniscule.