Be your own biggest advocate. I was too modest to really pursue professors for advice, help, or formal recommendation letters, hoping that if I was a good enough student, they would want to help me on their own. Everyone is busy and needs to be reminded of things, and people also tend to want to help someone who asks for their help. Also, I have since realized that other people were being aggressive and advocating for themselves, so by not doing so, I was putting myself at a disadvantage. This goes for job hunting and other things you'll do post-college, as well!