Quote:
Dress sharply
Don't dress for the job you have, dress for the job you want to have. Unless you plan to sling tacos on the corner for the rest of your natural life, start dressing and acting like your superior. The guy who puts on a tie tends to be trusted more than the guy wearing a greasy T-shirt. Appearance alone isn't going to get the job done, but it will grease the sale, and more importantly, it will help you meet chicks that you can take home to mom (or just take home).
That's a lot of great information, but I'd like to make one addition to the above section that I quoted.
I agree that dressing nice helps, but other styles shouldn't feel dismissed. I know some people, like myself most of the time, *do* enjoy the look of more ragged clothes. Just as a style decision. A bit of advice I once read that I've kept in mind ever since, is that the distinction from looking like a slob and looking sharp is how well the clothes fit you.
If you're going to wear a plain t-shirt, (make sure it's clean - dirty or stained clothes will just never work), but also look at how well it fits to your body. If you're going to wear more of a torn look, it's got to be well fit. Not necessarily 'tight,' but just well fit to your body. If your clothes are torn and you're wearing an XL sized shirt, and you're a medium or small, you're going to look like a bum.
It can really make the difference in appearing as though you've got it all together instead of looking like a mess.