I'd go back and tell myself about all of the bad on-the-job decisions I made so that I could have gotten rich during the 90's tech boom.
Oh, and I would have told myself NOT to buy that first house, and to stay at home with mom and dad for another 9 months after college and pay off my debt.
I could do both in the same trip, so where's the time machine? I'll be back before you know it. ;-)
M60s, VP180, VP150, QS8s, SVS 20-39PCi, HTPC, JVC RS45, Onkyo TX-NR709, Shakers