Look after your teeth. Once you turn 18, it's not free anymore. That means you pay. Go to a dentist once a year, but look online first and call to ask how much a check up costs. You'll be surprised at how much the prices vary. Yearly check ups will prevent serious problems.
It's who you know. Graduates are pouring out of universities with identical degrees. What gets you a foot in the door is not a degree or a cv filled with I was class rep! It is the people you meet who will help you out the most. Be good to them, help them when you can and the favour will be returned.
Expect to spend a lot of time photocopying in your first job. Its mind numbingly boring but it's a test. If you can get the basic stuff perfect, you will be trusted with more interesting work. Don't quit after six months. Stay in your first two jobs for at least a year each. Otherwise it looks bad on your cv.
Move out of your parents place. They'll love you for it. Then they'll miss you. So visit often. Do your best to be independent but don't be afraid to ask for your parents' help.
Celebrate your birthday every year. Use it as a chance to catch up with friends you see often, and those you haven't seen since your last birthday.
Learn to cook. A basic set of meals will make your life easy and healthy. Stock your kitchen with good quality equipment, and always buy when Briscoes has a big sale. Don't go food shopping when you're hungry and always take a list based on your planned meals for the week.
Have goals. Know where you want to be in five years. They will motivate you when you feel lazy and think about doing a half assed job. Goals provide your life with direction and answer the question of why you get out of bed each day. You don't have to write them down, just know what they are and think of them often.
Dress for comfort and dress for the season. Invest in at least one winter coat and actually wear it. Shop wisely and buy good quality clothes when they are discounted.
Choose a few charities you believe in and donate time, money or resources to them. Volunteer work makes you feel great and helps you meet people who are good at heart.
Always vote. It is your license to complain until the next election if your team loses. Be informed about local issues and don't just vote for the same lot your parents have always voted for. But never let politics ruin good friendships.