@endlesswonder - think about your personality and who you really are. Look through some listings online of personality types like this one: http://www.personalitypage.com/high-level.html - these tend to match up very well to the character descriptions included in the front of scripts and from other sources, such as stageagent.com.
To use some really simple examples off the top of my head (by the way, I would not recommend these songs for college auditions):
A guy who is quiet, reflective, and idealistic - “Corner of the Sky” from Pippin.
A guy who is practical, traditional, organized, and athletic - “I’ll Make a Man Out of You” from Mulan.
A guy who is people-oriented and fun-loving - “Oh, What a Beautiful Morning” from Oklahoma.
It was easier for me to think about guy-types off the top of my head.