What multivitamins are best for an 18 year old just starting to work out and eat healthy? I'm 5'7" and 140 lbs.

Healthy, real food! The current studies show that if you are eating a healthy balanced diet you don't need multivitamins. And they may do more harm than good. Concentrate on lean protein, lots of fruits and vegetables, and whole grains. The one thing you do not need, are "supplements" marketed to weightlifters.
Daily multivitamin. A regular daily multivitamin is all you need.... If even that. If you're healthy and having a good balanced with fruits, vegetables and protein, do not spend any extra money on vitamins or supplements. You'll be flushing money down the toilet. Keep up the good work on exercise and healthy eating!