Mr. Rob has a point; being taller isn't everything, and a lot of times working harder to compensate for a minor disadvantage just makes your skill stronger.
That being said, there are a few things you can do to make yourself
look taller.
Wear vertical lines. Notice how the guy on the left looks taller and slimmer than the guy on the right. I'm personally not a fan of stripes, and if you're not either then another option is
stick to monochromatic colors. When you dress up in one solid color, it doesn't divide your body into visual segments and helps make you appear bigger... or at least less short. Another thing is to
avoid baggy clothing. If you've read any of the fashion articles on the blog, you've probably already picked up on this. In general, baggy clothing makes you look lost inside your clothes and doesn't provide much for your appearance. Lastly,
good posture and
outward confidence are really going to help, too. Standing tall, puffing out your chest, all that basic fundamental stuff will go far. A short guy with good posture and a dominant appearance looks much more in control (and in a sense, "bigger") than a tall guy with bad posture and an inward appearance.
Hope this helps!