Meant to post this here: my own very unscientific tips for stretching money in an expensive city that I learned from being broke in the past.
Maybe some of my followers could find them useful. Feel free to add or comment. It assumes that one already has a place to live, with roommates, of course.

Books and information: libraries are wonderful. They have free ebooks too! And good for quiet study and work space with free internet without the urge to buy coffee at a coffee shop. They will help you do your taxes for free.
Most importantly, librarians are an excellent resource for just about anything. When we came to this country, the local library was the first place we were taken to.

Furniture and electronics:
Figure out when the curbside pickup is. Pray to garbage gods. When they grant your wish, don’t forget to sanctify your find with garbage-gods holy water – Lysol. Also, look near college dorms at the end of the school year. Tons of great stuff that rich kids discard.

Clothing: second hand shops, of course, preferably In poor neighborhoods, so they would not sell overpriced “vintage” stuff. Also, garage/tag sales in rich neighborhoods. Sign up for yahoo groups for wealthy neighborhoods you’re interested in. Nearly free furniture can be found here too.

Food: see if there is a food coop in your area. Markups are minimal, and the food is healthy and fresh. In return, you have to work there sometimes. Also, immigrant neighborhoods. It is incredible how much cheaper the food is in Bangladeshi and Turkish and Polish owned stores here.
Make your own food and bring it to work for lunch.
Drink tap water instead of beverages. Clean tap water is a vastly underappreciated first world achievement.
In a pinch: instant ramen. It saved Japan from hunger after the war, and it can save you.
Grow some greens, like basil in a pot in a sunny spot. It can last a whole year and makes food more interesting.

Art (this is why you tolerate this ridiculous city, right?): galleries are usually free, and in some cities museums are, too. NYC has a free NYC Id program that allows for free membership in many city museums. Learn about free outdoor concerts and theater that your city has. Check your local equivalent of brokelyn.com

Going out with friends: avoid it, unless they are paying. You can have just as good of a time at home or playing board games. Sometimes it’s important though. If you must drink alcohol, bring alcohol in a flask and surreptitiously make your own cocktails with the cheap juice or coke you ordered from the barkeep. If you forgot your alcohol, stick to cranberry juice and pretend you’re religious or headachy. You are there for the company, not to get wasted.

Side jobs: if you have the time, taskrabbit and local neighborhood bulletin boards are good ways for quick side projects. Pet sitting, dog walking, painting, temp office work, and babysitting, and senior-people care could bring some extra money to help out. Make sure you collect references to expand your client base. Also, teach what you know via Brooklynbrainery.com or your local equivalent

Managing cash flow: in U.S. only: get a Fidelity Cash Management account. It is free, you can deposit checks with your phone, and they refund ATM fees everywhere! The only downside is that they won’t lend you money because it’s not a bank – fidelity is a stock-trading service. But you don’t have to trade any stocks.
To borrow money, find a local credit union. There might be one affiliated with your school or neighborhood. They are just like a bank but they are not out to make money for shareholders and so they won’t be greedy. If you are not sure, you’d be surprised what your librarian might know about options in your area. Just ask.
Find out if you could be eligible for any government programs. Look on your local government website. Check your local elected representative’s office. In the U.S. they always have them in your neighborhood – you can just come in and talk to their staff – they sometimes have free education events like that. I’m sure it works similarly in all other liberal democracies. It could be food or housing subsidy, or free or reduced healthcare. Safety net exists for all of us, so take advantage of it if you must.

If you are really strapped for cash, ask your parents and friends. If that’s not an option, ask your credit union or, ahem, bank. If not, use your credit card – but only if you know you can pay it back. When you get your check, pay back the highest interest debt (credit card!) first – as soon as you can. Each day accrues ever increasing interest! Pay back the banks before you pay back friends. They will understand.
For school loans, check out government deferment programs. Google it or ask your librarian. But only trust .gov websites as well as known media websites like Forbes.

Haircuts:
Salonapprentice and Craigslist has listings for well trained people who would gladly cut your hair for free either as a part of their advanced and supervised training or to accrue experience hours they need to graduate to their next level.

Networking and meeting people and finding serendipity:
meetup.com is incredible for just about anything. Also, couchsurfing.com . There are travelers in your area who are just as curious and broke as you are.