It has been said many, many times, over and over again. Others will take you as seriously as you take yourself. How you treat yourself, how you groom yourself, how you dress yourself, how you respect yourself, will speak volumes to those around you. And trust me, if you show everyone around you that you don't give a rip, then they won't either.
Here's what Randall S. Hansen, Ph.D., and Katharine Hansen, Ph.D., had to say about looking your best with regard to making a lasting positive impression:
"In categorizing people, we all take shortcuts, and first impressions about people often turn into long-term perceptions and reputations — which are good for people who make positive first impressions (the halo effect), but bad for people who make negative first impressions."
So get into the know-how and invest some time and effort into producing a strong, lasting impression. It will serve you well, you can be sure of it.
~j