Determine how much you are going to save first. Then determine where you can spend your money. If you're living with your parents, try to build an emergency fund of six months income. The simplest way is to put half of your income in the emergency fund for a year.
Try to save at least 10% of your income for retirement. The earlier you start this, the longer you'll have to let the magic of compounding work on it. If your employer offers a 401k with a match, do that first. If not, consider an IRA. You probably want to do a Roth now (because you probably pay little in taxes so the deduction from a standard IRA won't help you).
After the year, you'll have an emergency fund. Work out how much money you'll need for rent, utilities, and groceries when you're on your own. Invest that in some way. Pay off student loans if you have any. Buy a car that you can keep a long time if you need one. Go to night school. Put any excess money in a savings account or mutual fund. This is money for doing things related to housing. Perhaps you'll need to buy a washer/dryer. Or pay a down payment on a mortgage eventually.
Saving this money now does two things: first, it gives you savings for when you need it; second, it keeps you from getting used to spending your entire paycheck. If you are used to only having $200 of spending cash out of each check, you will fit your spending into that. If you are used to spending $800 every two weeks, it will be hard to cut your spending to make room for rent, etc.