When should I start applying to jobs?

When to send out your resume all depends upon the job you're looking for and its hiring schedule. For example, many of the types of professional services jobs that offer training programs (e.g., Investment Banking, Consulting, etc.) most likely already have had rounds of interviewing and probably already know who's going to be working for them in the fall. That being said, if you are interested in this type of an industry, there's no reason you can't just cold call a company you'd like to work for and see if they're still accepting applications. Better yet, speak to your career center and search your network to see if anyone could connect you with an individual at HR to sneak you into an interview process.

If you're looking for most other types of jobs, while they most likely won't begin their hiring process for another few months (ie. around April/May), there's no harm in reaching out now. One of the toughest parts of applying for a job is getting your resume in the right hands. Of course if they have an application submission page on their website then it's a breeze, but many of the companies that will hire later in the year sometimes make it more difficult for you to find who to submit an application to. So, start researching now. Tap your personal network. Tap your alumni network. Also just reach out to the company. Sometimes it will take a few calls to get to the right place.

And last but not least, of course if a company has an application date that's down the road, you don't necessarily need to jump the gun and apply today. While you certainly can - they put a date up there for a reason. In the meantime, however, network to some people in the company (eg. use LinkedIn's degrees of separation tool) so that when you do apply, your resume gets preferential treatment.