Alot of good advice already and good for you for even thinking about this stuff at 18. Definitely agree with investing early and often. Also, have balance in everything. Tomorrow is not guaranteed.
I'll tell you what I've told my two boys. Do something that will one day allow you to be your own boss and, if possible, that makes money even if you're not there. Most of my buddies I grew up with own their own businesses (contracting, plumbing, electric, tile, dentistry, law, finance, accounting, etc). By and large, those people are financially set by age 50 or earlier and have the flexibility and time to enjoy life while still making a very good living. It takes some risk on your part and can be very lean in the early years, but it can be worth it in the end. Just a thought.