When it comes down to it, almost everyone lives on a fixed (or limited), income. But the term usually refers to people whose incomes are not high enough to allow them to do whatever they want. I am going to list a few things I have learned in my several years of living on a $1000-$1200 per month (USD) income.
Utilities
First let's look at how to reduce your electric bill effectively, without going to insane measures (like my parents do). We will start with light bulbs. You need to replace all your light bulbs with the lowest wattage bulbs that you can handle. I would suggest trying out a 30 watt bulb first (I can handle them), if that isn't enough for you, then work your way up until you find something you are comfortable with. You should also make sure that you don't have any of those fixtures with multiple bulbs, you don't need them. I have a lamp that takes three bulbs, and I am just as comfortable with only a single bulb installed. You may also want to look into "energy saver" bulbs, which are fluorescent lights designed to go into standard light fixtures.
Now let's move on to other electrical items. Did you know that turning your computer on and off all day long uses more power than simply leaving it on (my parents do this to "save power", they don't "get" the concept that it uses more power booting up, than sleeping, so they turn it on and off 20 or more times a day). Simply set up your power management on your computer, and only turn it off when you won't be using it for at least 8 hours or more. You should also get in the habit of turning off your monitor, because you can save a little money there.
You should also look at your refrigerator, as it uses more power than just about anything else in your house. If you live alone, you can probably replace your huge power hungry fridge with a small dorm size one, at a substantial power savings. If you are like a lot of young people, then you probably don't have much in there beside condiments anyway (which usually do not need to be refrigerated in the first place).
Most other consumer electronics (VCRs, CD players, etc), only use minimal power when not in use, so you don't really have to worry about obsessively turning them off and on. There is an exception to this rule, anything that gets hot when it is on and not in use, is eating a good amount of power, so turn it off (my old satellite receiver did this, although you really don't need satellite TV in the first place).
Now let's look at your oven. I am not suggesting you get rid of it, but I am suggesting that you minimize use of the interior (the "oven" part as opposed to the "burners"). When you do use it, why not make several dishes at once (saving the rest for later), to avoid the expensive (in terms of power or gas depending on your oven), warm up time.
Turning down the temperature on(and insulating), your water heater is a good start to saving on your gas (or electric, depending on your water heater), bill. You can also save money by reducing the temperature on your thermostat. Instead of giving you a "number" to shoot for ,which is probably wrong anyway (the thermostat at my work isn't at a comfortable setting until it reads 90 degrees Fahrenheit, many thermostats are wrong), I am going to suggest a different strategy. Cover up those temperature numbers altogether, then slowly (over the course of a week), reduce the (now hidden), temperature. When you finally get to a point where you are cold, then turn it up just a notch, and leave it there.
You can live without air conditioning (unless you are elderly, or have other medical needs), it only takes some getting used to. Not using your air conditioner can save you big bucks on your electric bill (and I do mean big).
Did you know that people lived without cable television, satellite television, cellular phones, or pagers as little as 10 years ago. You don't need any of these, and don't make excuses as to why you do. Nobody really had any of that stuff twenty years ago, and ten years ago they were all rare (with the exception of cable), so there is no reason why you should "need" them now. All four of those are monthly bills that can be eliminated altogether.
Finally, you should examine your home to see if you have any other power (or gas) hungry devices, such as external house lights. I myself have a few arcade games, and to reduce their power consumption, I have wired separate on/off switches for the monitors (as the monitors eat many times more power than the game itself does), so I can switch off the monitors when the games are not being actively played (it isn't good to turn the games themselves on and off all the time, it reduces their life expectancy severely, but the monitors can be safely turned on and off all the time).
Food and drink
The first thing you have to do is stop going to restaurants entirely. If you find yourself in the situation where you must go to one, then simply order water, and the cheapest side dish they have available (and then eat when you get home). To really save money on home food preparation you should frequent your local "cheap" supermarket (my area has Save a Lot and Aldi, but you probably have different stores). You should learn to get used to the inexpensive food items available at these stores. You should also realize that you do not have to eat meat every day (or cheese), as they are some of the most expensive food items anywhere. Next you should stop drinking soda and beer all the time, just drink water, it is effectively free, and you will get used to it (alternately, you can drink tea or Kool Aid, as they are dirt cheap).
To further save on food costs you should learn how to effectively mooch. Never pass up a free meal, be it from friends, relatives, or even from employee functions at work. Everyone of these meals is a meal you didn't have to pay for, and this can add up to big savings when repeated often enough.
Consumer Goods
This is where a lot of people waste tons of money. You often never realize it because it is always in such small chunks, but it adds up big time. I am going to list a lot of areas where young people (my target audience), waste a lot of money, and offer alternative solutions to stretch those dollars much further.
- Music
How many CDs do you have? 20? 50? 100? Do you realize that you probably spent $1500 on that collection of 100 CDs? There are two free music solutions right in front of you. The first is the radio, chances are there is a local station that you may like. The second is your computer, there is a whole world of free (legal) music out there in mp3 format for you to download at no cost to you (even more if you "pirate" music that is not supposed to be freely downloaded). You should also consider cassette tapes and records. I can buy 150 used records at my local thrift store for the cost of a single new CD. That is an entire music collection for the cost of a single Limp Bizkit CD. Now you aren't going to find the latest hits on record or cassette at your local thrift shop, but there is nothing wrong with older music, good music is good, no matter when it was recorded.
- Movies
Stop wasting money buying expensive DVDs and video tapes. Watch what comes on television. Use your VCR to record good programs and movies for later viewing. You can record thirty movies for the price of a single DVD, sure DVDs are cooler, and have special features and all that jazz, but you will get more enjoyment and entertainment out of those 30 movies you taped from the television (I promise). You may also be able to freely borrow a wide variety of videotapes and DVDs from your local library. In fact, my mother purchased a DVD player simply because her local library has switched over to ordering DVDs instead of video tapes.
- Clothes
You do not need to be a fashion plate to be a useful member of society. I spend almost nothing on clothes (save for the occasional thrift store visit or new $10 pair of work pants), yet I still have a job, go to parties and other social gathering, date, and even have sexual intercourse, all without one pair of $99 Tommy Hilfiger jeans. As a matter of fact, I lead a normal fulfilling life without a single pair of $60 shoes (my most expensive pair was $15). You can do this too, it doesn't even take much effort at all.
On a side note, my best friends marriage failed as a direct result of his wife’s inability to stop spending an average of $400 a month at Old Navy (purchasing endless variations on the exact same two or 3 outfits that they sell). When I helped them move in with me (before they split up for good), I personally moved 12 large bags full of clothes that had never been worn, they even still had the tags on them (total price on all the receipts in the bags added up to over $3000). Don't let this happen to you.
- Video Games
This probably isn't a problem for most of you, but if you have a shiny new Playstation, Nintendo or X-Box (or simply have a shelf full of PC games), then you should read this section.
The first place to look for discount gaming is right there on your personal computer. There are literally thousands of free games available for download (about 25,000 more if you include abandonware, MAME and other emulators which are of arguable legality). It would take you 60 hours of gaming a week for several hundred years to possibly get sick of all these free games, so why are you buying games to begin with.
A new console system and one game are going to run you about $350 USD (prices based on current eBay sale prices for Playstation 2). Do you know what you could have for that kind of money? You probably don't, so let me give you a few examples. For about $300 you can buy a NES top loader with 100 games (the top loader is the Nintendo that didn't fail like the others did). For $250 you can buy a Sega Genesis system and 200 games. For that same $350 you spent on the Playstation, you could buy an Atari 7800 and about 300 games. For about $350 you can buy a real live arcade game, and about 12 extra game boards to go inside. Now look at all those options, is the Playstation 2 the best one, I ask you?
- Other items
For other purchases learn how to use the thrift store. You can buy plenty of nice used items at only a fraction of the cost of a new one. The most notable thing in this category is furniture. Furniture from the thrift store is an order of magnitude cheaper than the prices at a normal retail outlet, and at a thrift store you can buy furniture that isn't made out of particle board (and thus won't fall apart in five years). Every piece of new furniture I have ever purchased is in horrible condition now, yet all my thrift store furniture purchases (although some pieces are up to 50 years old), are still in excellent condition. They simply don't make furniture like they used to (well they do, but the prices are outlandish). Carefully selected used furniture will outlast almost any of the particle board-screw-together monstrosities that you can buy at your local Sears, Wal-Mart, or Zellers.
Entertainment
I am going to be brief on this subject, as I really only have one piece of advice to give. That is advice is to go to parties instead of clubbing, movies, skydiving, or anything else. Parties are almost always free (if not, then don't go), and will often have free food and alcohol to boot. Not to mention the fact that your chances of finding a boyfriend/girlfriend/sex partner is much higher at a party than at a club or bar (that has been my experience at least, comparing the large amount of women I have "hooked up" with at parties to the exactly zero women I have picked up in clubs and bars, of course your mileage may vary).
In closing, when trying to limit your expenses you should look at every expenditure, and ask yourself "Is this needed?", and if so, try and think of a cheaper way to do it.