Before you submit papers, reports, research projects, essays, poems, art projects, etc. Many sponsors want to see a sample of your work. Join clubs, organizations or associations affiliated with your fields of interests or talents. Sponsors like to see students giving of themselves. Have the person in charge of the program or project write a letter or sign an affidavit to document your time.
Many sponsors ask for some sort of documentation.
It is difficult if not impossible to go back and document a community project you participated in 2 years ago.