Although unrelated to biology, working as a Peer Career Adviser for five semesters has taught me invaluable techniques and tips for how to create excellent resumes, cover letters, personal statements, networking notes, and everything else, and I definitely could not have gotten into PhD programs without that knowledge. As for advice, I have three pieces to share:
First, grades are not everything. Those students who maintain amazingly high GPAs but who don't have time for anything else will not be competitive, so make sure you're well-rounded yet focusing yourself on your long-term goals.
Second, go to the Career Center! They have great advice for whatever stage you're at, and will make a flawless resume.
Finally, it's okay to not know what you want to do. I was lucky to know at a young age, but it's not awful if you do not know. College is a time to try everything out, so take advantage. Also, the Career Center has great resources to show you what jobs are out there, and what you can do with your major.
Read more 2013 Senior Success stories here.