I think just every guy has been guilty of sitting down in a buttoned jacket at some point or another. While it may seem harmless enough, this is a major fashion mistake that should be avoided. So, what's the problem with sitting down in a buttoned jacket? Well, it causes the midsection of the jacket to bunch up, resulting in a messy, wrinkled appearance.
Color-Code Your Belt and Shoes
Another essential fashion rule that all guys should follow when wearing a suit is to color-code your belt and shoes. If you plan on wearing a pair of black loafers, for instance, match it with a black belt. Alternatively, if you plan on wearing a pair of brown shoes, wear a brown belt -- you get the idea. Wearing mismatched colors will only hurt the aesthetics of your outfit by making the accessories clash with one another.
Wear the Right Socks
You can't wear everyday gym socks with a suit. Instead, you need to wear thin, "dress socks" that match the color of your suit pants. Most department stores sell dress socks for a couple bucks a piece, which is a small price to pay for the value they add to your outfit. Just remember to choose an appropriate size so your legs aren't exposed when sitting down. If your socks are too short, it may leave some of your legs exposed when sitting down, which is never a good thing.
Tie Should be Darker than Shirt and Jacket
When wearing a suit, make sure your tie is darker than your shirt and suit jacket. If it's lighter, your suit will look off-balance, as the tie will seem to fade away without being the focal point. The bottom line is that your tie should be darker than your actual shirt and suit jacket.
Match Your Pocket Square With Your Tie
While not required, adding a pocket square to your suit will enhance its appearance to create a more visually appealing outfit. However, you have to choose a pocket square that matches the color of your tie.
Pants Should Reach the Top of Your Shoes
What size pants do you need? A good rule of thumb is to choose suit pants with a hem that stops at the top of your shoes, no more or no less. Wearing pants longer than this will result in a baggy appearance, whereas pants that are too short are equally as bad.