Rule One: Fit
The fit of your clothes can make the difference between looking stylish and looking like Ross from the first season of Friends. Of all the style ‘rules,’ fit gives you the most bang for the buck. This is because you already have to buy clothes. And because clothing manufacturers make clothes in different cuts and sizes, all you have to do is pick the something that fits properly.
Before you go off shopping all willy-nilly, you need to know what well-fitting clothes look like. To this end, I suggest looking lots of photos of well-dressed men. You can find great examples of a slim, easy fit in the J.Crew catalogue and website. Additionally, Sid Mashburn and Scott Schuman are both examples of impeccably dressed men; just google search these guys and you’ll see what I mean. If you want a positively exhaustive explanation of fit, buy Dressing the Man by Alan Flusser, you won’t be disappointed. Admittedly, looking at other men on the internet sounds a little strange, but this is simply how we learn–by imitation.
Get measured. If you haven’t been measured for a suit and shirt, go and get it done. You can have your measurements taken at any tailor, or medium to high end retailer, like Nordstrom or Brooks Brothers. Having your measurements will help you immensely when in comes time to try clothing on. Its very likely you’ve been wearing a large your whole adult life when you should have been wearing a medium in slim fit, your measurements will illuminate this for you.
Try clothes on before you buy them. I know, it’s annoying, you have to take your shoes and pants off, but this is literally the only way to make sure the clothes you buy fit you. Don’t buy anything before you try it on. Repeat after me, I won’t buy anything before trying it on. The key here is patience. Know that most of what you try on won’t fit properly. If you try on ten pairs of trousers and get one to fit you, you’ve had a good day. The same goes for shirts, shoes, and everything else. Patience is absolutely key. Learn to walk away from an item, even if it’s on sale. The obvious exception to this rule is online shopping. The best you can do is carefully read their return policy before ordering, making sure to follow their rules once you get the item in the mail, that way if it doesn’t fit you can return it for a refund. Some newer online retailers offer generous shipping and return policies, Everlane, Rancourt, and Bluer Denim are great examples of this trend. Others, however, are rather draconian, not accepting returns on sale items. Be mindful of these policies and do your best.
How exactly should your clothes fit? This is a tough question to answer because it depends so much on your body shape and your lifestyle. Though this is a massive question with a whole lot of answers, there are some very simple guidelines that will help almost every man. A shirt’s shoulder seam should fit at the apex of your shoulder. If the seem is down your arm, the shirt is too big, if it’s in toward your neck, the shirt is too small. Shirt sleeves should end at the hinge of your wrist when your arm is bent at 90 degrees. The shirt’s collar should neither be so tight it’s cutting in, nor should it be gaping at the neck. The body of a shirt is a little trickier to judge. I like my shirts to be slim but not tight, a (very) little billowing hasn’t killed anyone. The slimness of your shirt should be in proportion to the slimness of your trousers. Trousers should be tight enough to stay in place with out a belt but not so tight…well, you’ll know if they’re too tight. Your trousers should be long enough for a full, half or quarter break with your shoes on; they should not, however, be pooling around your ankles. Though these are some of the big, obvious easy tips, there are a hundred other small rules concerning this topic, and again, I urge you to look to Dressing the Man for further advice.
dapper and down-market 
