The best way you can cut down on debt and make a comfortable life for yourself is to start earning money as soon as possible. There are many ways you can do this while a student, although some are more efficient than others. You will need to find methods that don't interrupt your busy lifestyle or get in the way of harming your med school application. If you can't handle a part-time job while also studying hard to get good grades and volunteering or shadowing a physician, then you should get rid of the part-time job.
I'm not trying to say that it's not good to have a part-time job. It can be a great way to make money and it provides a (tiny) bonus on your application. However, if you seriously want to be a doctor then you need to think long-term. You will make much more money in your lifetime if you lose the job and do everything you can to make sure you get into med school.
And I understand that there will be some students that absolutely need the money to pay rent or eat or pay their bills. My recommendation is to try alternative ways of making money that require less time and don't get in the way of your duties as a pre-med student. If this isn't feasible or you just make better money with your job, then you might as well keep it. Try your best to manage your time well and still make yourself a stellar applicant so you can get into med school.
Here are some different ways to make money while in school:
"Donate" Plasma
Donating plasma can be a great way to pick up extra cash while giving very little effort. If you don't mind a little bit of pain and you are willing to sit around for an hour or so, then you can make some decent money donating plasma. Most plasma centers let you donate up to twice a week and pay 20-30 dollars per session. You can make hundreds of dollars a month just selling your plasma! Make sure you drink a lot of water and eat enough to help prevent weakness and dizziness.Tutoring
Whether or not you are hired as a private tutor or work for a tutoring organization, tutoring can be a great way to make money because it plays to one of your biggest strengths: your brain. If you are a pre-med student, chances are you are pretty smart and/or a hard worker. These attributes make you the perfect tutor. You an choose to advertise yourself (by putting signs around campus or an advertisement online) or work for an established tutoring organization.
Use what you are good at. If you are particularly talented in chemistry, then maybe a general chemistry class is what you should tutor in.
The benefit of being a private tutor is that you can pick your own price. The downside is that you must find a way to advertise your services and bring in customers. Joining a tutoring organization typically won't allow you as much freedom to determine your wages, but it will be much easier to find customers. Ask around to find out if your campus has an organization dedicated to tutoring students already and if they are accepting new tutors.
Participate in Psychology Experiments
Find your college's psychology department online or ask around to see if there are any psychology experiments that will pay students to be subjects. Professors are always in need of subjects for various psych experiments and are often willing to pay for your time.
Sell Stock Photos Online
Do you have a digital camera and a knack for photography? Do people often comment on the beauty of your photos? Many sites are available (such as shutterstock.com, fotolia.com, and istockphoto.com) that sell stock photos. You can upload your photographs to this site, and when someone buys one of your photos, you get money.
Sell Your Notes
Some of you may have a bit of a moral problem with this one. If you don't want to feed someone's habit of extreme laziness and think people should do their own work to pass the class, then you are less likely to sell your notes. However, there are some people who legitimately miss class or aren't good test takers. These people can benefit from notes that cover all of the important topics covered in class. You are unlikely to make a regular income with this method. It will only get you a few dollars here and there, unless people keep wanting to buy your notes.
Sell Your Stuff Online
This one is pretty obvious but many people neglect it because they don't realize how much money they can make with just a little bit of work. Gather up some old stuff you don't use at home, and sell it on eBay or in a yard sale. Depending on the amount of your belongings you are willing to part with, you can make some quality spending money that will last you several months.
Are you sure you can't find anything to get rid of?
Or if you enjoy selling your things but are running out of things to sell, you can hit up local yard sales or thrift stores and flip items for a profit. This is fun for a lot of people because they get to shop while also making money.
Amazon's Mechanical Turk
Mechanical Turk is a website where you can sign up and perform easy tasks in your internet browser to earn money. At best you will probably only make a few dollars an hour, but it can be convenient because you can work on your own time at the pace that you want. I used it for an hour or two and made about 4 dollars. It can be a good way to pick up a few extra dollars if you don't mind the tasks you have to do.
Sell your Services Online
ChaCha is a service that allows people to text questions or ask them online and have them answered. They will pay you for your answers. Student Of Fortune allows students to ask homework questions and put a price on them. The best answer for this question earns the money offered for the question. You can sign up for these sites online and earn some money by answering peoples' questions.
Hopefully you can use some of these methods to earn yourself some extra money. Whether you already have a job or not, you can use these alternate ways to earn some spending cash.
Probably the best overall book when it comes to medical school admissions. Highly recommended. 
Another very strong med school admissions book.
The Barron's MCAT review book. It is one of, if not the best MCAT review book out there.
700 MCAT flash cards designed to reinforce your knowledge in the fields of chemistry, organic chemistry, physics, and biology.