Tracking your expenses and money is probably the most important think you can (practically) learn at your age. If you already have a job or some source of money coming in, then you should learn to balance wants, needs, savings, and bills now. My personal philosophy is to always have at least six months worth of savings in a high interest savings account. This way, if I ever lose my job or have a disaster strike me, I will have six months worth of relief to fall back on and get myself back into gear. Of course, time is money and money depreciates over time, so always having that money in the bank is nowhere near as good an investment as other things can be, but the important thing is that I have a reliable and available source of backup income when I need it. Your rent should never cost you more than 30% of what you make, and you should always have a fraction of your income going into savings so that you are not tempted to spend it. Another good piece of advice is to work out your bills so you can pay them all on the same day. If you can afford it, at the first of the month along with rent. If not, then in the middle of the month to help ease the weight of the bills. Having your bills paid on the same day not only gets you into a routine for getting them paid and out of the way, but it also keeps you from forgetting to pay certain bills and allows you to manage your money better. With that, you should be left with about 10-40% of your income remaining for you to do with what you want. It should go without saying that "a penny saved is a penny earned", and the more you save the more you can afford when the important things come your way. Lastly, building credit. Ask your parents how to best do this and look around for yourself, as I am not a financial wizard. My best piece of advice is to pickup (with your parents' help) a basic credit card and use it to pay for your gas only. At the end of each month, with your bills, either pay off the entire balance (since you would have spent it on that gas anyway) or pay 10-20% on top of your "minimum payment due". Some credit companies don't like it when you pay everything off immediately, but if you are always spending it should still build your credit. NEVER MISS A PAYMENT!! By paying 10-20% on top of the minimum due, the credit company sees you are paying more than the minimum, but still have a balance for them to make interest charges off of. It's not a fair world, but if you have bad credit you won't get very far in life. Because you likely have no rent right now and no major bills, it would be a good practice to start funneling away 30% of your (existing?) paycheck into a savings account in imitation of rent, 10-20% into the savings account in imitation of….savings, 10% into the savings account in imitation of bills, and then 5% into the savings account in imitation of miscellaneous expenditures. This way you have a great start on savings, learn to manage your money before you get in over your head, and still have plenty of money to spend on whatever you want. OH! I don't know too many high interest banks out there, but I know ING Direct is pretty decent and I believe it has a 4.3% fixed interest rate for savings. They also have checking accounts with a decent interest rate, but I prefer a more available bank for my checking accounts.
Most kids your age are considering their first car about now, correct? Assuming you do not have one yet, I would begin learning about cars at the least. What you want to avoid is using your "first car" savings/money-from-parents to buy a crappy car that will cost you more than it's worth. This is where patience would be a great benefit. Either save money and get a cheap car that will cost less on insurance and gas, learn to keep it up and running with basic maintenance knowledge, and then sell it when you are older to buy a new(er?) car of your preference OR wait it out and ride your bike/tram/train/bus to work and school until you can afford a nicer / new(er?) car. A large portion of your life will be "spent" making payments to something, so a car payment early on would help you become accustomed to the real-life finances – but I would avoid it if you can, personally. Building credit would be better elsewhere I believe. I personally believe a cheap first car is always best. Why? Because the value depreciates terribly over the years, and when you are young you tend to make impulse decisions (like buying an "awesome" car) that you live to regret further on down the road. Depending on the used car you buy, you can resale it a few years later for fairly close to what you paid for it as long as you keep it in good shape and don't drive too much. This way, when you are older and have a nicer job and family you can afford to buy a practical nice car that you like and will last through the years as opposed to getting a car that doesn't fit your needs once you become an adult, which would lead to your losing a lot of money selling your highly depreciated "new" car. (Not to mention losing money on the interest payments there).
Think for yourself. Whether it is finances, cars, school, careers, housing, location, women, politics, or anything else out there – learn to think for yourself. I am not saying you cannot already, I am just saying be wary of anything and everything you hear and read, and try to see every angle before your jump into it. Some of the worst mistakes you can make are made because not enough thought or research was put into it: passing up a good job, taking a bad job, getting stuck in a contract, taking a bad loan or interest rate, getting a bad car, voting for the wrong person, going to the wrong school, picking the wrong career, or even choosing the wrong paint/color for your living room. Plan out what you want, and pursue it. Don't "settle" or be lazy. If you map out your career and education now, take care of your finances, and figure out when and where you want to be when you reach a given age, then you will find yourself in a much better situation than half the population in America once you get there. On the other hand, if you waste that time and dawdle too much then you will still be stuck in your parents house at 23 years old wishing you had been more consistent and steadfast in your studies.