With my career choice plus my total lack of family support I've always had to be very good with money. Plus having worked for Mastercard for so long, I learnt a lot about financial management.
The best of all advice is to adopt a philosophy of peace in simplicity. As JL notes, living green is financially beneficial, but it can also be very peaceful to look at what you really need in life. It's amazing how little you need to be healthy and happy. Taking on a DIY attitude toward everything is very empowering. Most communities have DIY organizations, and there's tons of tips on-line and at the library about this. Buying used clothing, especially if you can deal with basic alterations, is a great way to save. It's amazing how many hardly-worn cast offs there are out there!
I definitely agree with the credit card advice. If you have a card call the company and put a block on it, then either cut it up, or freeze it in a block of ice (that way you have to unthaw it and put a lot of thought into why you're using it.) Don't cancel the card - having and maintaining a card is good for your credit rating. Only unblock it if it's an actual life or death emergency involving your health.
Living expenses - it seems to sound like you're already living in a situation that should be pretty cheap, but definitely investigate your options. We've chosen to live in a poor neighbourhood because it's so much more affordable. Yes it's more dangerous here, but even with the cost of high-quality alarm monitoring our mortgage payment is lower than our rent used to be. If your city's much like mine, the shitty neighbourhoods are also the ones near the city centre, which means access to public transportation, which takes me to my next point...
The best thing I've done to cut costs is to drastically reduce my dependence on a vehicle - walk, bike, use public transpo, car pool - put every single option before using a car. Having made this change I went from fueling up twice a month to fueling up 4-5 times a year (this saves me about $700 a year, not even including the reduction in regular maintenance costs). If at all possible, find out if there are cheaper insurance rates for vehicles only used for "pleasure" and/or parked/dormant vehicles. I have my car registered for "pleasure" during times when I need it and switch it to "dormant" to cover vandalism and theft for 5 months of the year. My insurance is pretty high, so this saves another $300 a year. Yeah, it's not fun to be walking out in bad weather, but the added benefits of the extra exercises I get are pretty awesome, and I'm pretty happy with the stress reduction of not having to deal with traffic.
Lastly, if you have a skill you can make extra cash off, put yourself out there and do it. Odd jobs are usually pretty fun, and even when they're not, they're usually short term enough that it doesn't matter. If you're crafty, if you have fix-it skills, if you can pet sit... anything. Market yourself to your bud's, around the neighbourhood and/or find something on-line. I made money pet sitting, writing for a few on-line magazines, delivering fliers, editing papers... all sorts of odd jobs. One thing that's really fun that I didn't get into but that was a way friends made money is by advertising yourself as a conversational English instructor by posting ads around university campuses with large foreign student/ESL populations. Many of these students have particularly come to North America to learn English, and you obviously have the skill they need already. You can meet you students in public places like grocery stores, coffee shops etc and make your lesson about the world around you.