I make only $10.50/hr at my job (35-40 hrs/week), yet I make enough money to live on my own (Apartment rent is $635/mo) and pay for my college tuition completely out of pocket, buy food, pay bills, etc., while still having about $50-100/month in spending money.  Its really not hard.
I think the thing most people waste the most money on is food.  If you're smart, you can easily feed yourself for under $3/meal.
-NEVER go out to eat at a sit-down restaurant except for special occasions.
-Keep fast food to a minimum.  For how much you're spending on one meal, you could probably buy two or even three meals.
-Don't order delivered pizza.  Getting a delivered pizza will probably cost you $15 MINIMUM once you add the delivery fee and tip.  For those $15 you could easily buy THREE frozen pizzas from the grocery store, possibly up to 6 if you buy the cheaper brands.
-Try the store brands of all your favorite foods.  If you're convinced that there IS a difference, have a friend help you and give you a blind taste test.
-Avoid buying soda.  If you really don't want to just drink water and feel that you really have to have something sweet, buy a variety of Kool-Aid packets and a pound of sugar.  It will last a long time.
-NEVER EVER buy bottled water!  Its been shown time and time again that bottled water is not magically safer or cleaner than tap water.  It is not better for you.  And in fact, most bottled water makers are simply selling you tap water in a bottle. 
Video link! If you really want to add some extra filtering to your water, get a filter from Brita or Pur.  I have a Brita pitcher and I love it!
-Force yourself to eat your leftovers.  Living alone, most packages of food are meant to feed up to 4 people.  I have a big appetite, so I end up eating half the package, but I make sure to eat the rest either later that day or the next day.
-If a food dish has microwave instructions, use them instead of the oven instructions.  A microwave will use less power to heat the food than an oven will.
There are also a lot of habits to do to save money...
-Turn off the lights if you're not in the room.  Right now, I have only one light switch on.  Also, replace incandescent bulb with compact fluorescents.  While they cost a few dollars more, they not only last longer, but consume a small fraction of the power.
-Drive conservatively.  Accelerating quickly not only destroys your fuel economy, but it often doesn't save you much time, if any at all, depending on where you hit the red lights.  On the highway, wind resistance grows exponentially with speed.  Most cars are designed to get the best fuel economy at around 60 mph.  You can go up to about 70 and only lose a couple MPG, but past that and it plummets.
-Trade in that SUV for something more economical.  You can easily cut your fuel costs by half.  Depending on how much you drive and your driving habits, the savings in gas costs could actually pay for the car.
-Try to find a home near your workplace, or a job near your home.  If you have to drive an hour to get to work, you're doing it wrong.  30 miles to work and 30 miles home, even if you drive a car that gets a decent 30 mpg, and with gas prices at a low $2.50/gal, you're going to spend $100/month on gas just to go to work 5 days a week.  I live about 3 miles from work, and average 26 mpg city/34 highway (Car is stickered at 24 city/32 highway!), and only spend $30/month on gas.
-Pay off debt before putting money into savings.  People like to think that they're saving for the future by putting money into a savings account, the money is better off being put towards paying off a high-interest loan than sitting in a low-interest savings account.  Do the math and you'll easily see why.
-Turn down the heater and put some more clothes on.
I'm sure I'll think of other things later.