One major way to stand out is what you bring to the table.  If you do internships, be sure you put them on your cover letter and on the resume.  Show the employer that during your Sophomore year you did an internship or showed dedication to your chosen field.  Working fast food or a retail store is a sure sign to an employer that you were not dedicated....especially if it's as late as your Junior year. 

When interviewing look the interviewer in the eye.  During a telephone interview speak clearly and sit in a slightly uncomfortable chair.  Pretend you are in front of your interviewer.  Always have your resume in front of you.

Finally, when interviewing, ask lots of questions about the firm's culture, mentoring process, and the average work day.  Interviewers like inquisitive candidates. 

Another thing I would suggest to take leadership roles in student organizations.  None of your peers have time, but those who make the time to go above and beyond stand out!