There are some people that believe that all clothes are made equally. They believe that if one person can wear one thing, so can someone else even if their body type is completely different. Technically, you can wear whatever you want if you don't care, and that's fine, but if you want to dress for your body type and tailor your clothes and your style to you, read on.
The *Really* Tall Guy
Description: If you reside in the US, the average height for males is between 5'9 and 5'10, but typically one is considered to be a really tall guy around the 6'3+ mark.
Advice: If you aren't a fan of your height, there's not much you can do about it, but visually if you'd like to give off the illusion that you aren't as tall as you actually are, avoid any patterns and designs on your clothes that go vertical like pin stripes or the monochromatic look that tends to emphasize length. You are a rare breed for which horizontal stripes and patterns are your friend. You want to chop the line of your frame with things like a brightly colored belt, cuffed jeans/sleeves, larger accessories, layers, color blocking, etc.
One of the major problems tall guys face is when the sizes get bigger, they tend to get wider as opposed to longer which if you are physically average sized for your height or in particular, a thin tall guy, these things look dumpy on you and can swallow up your frame or they don't provide enough coverage (crop top anyone?). Average sized shirts will never fit you...they just won't. You will need to either find stores that offer up longer length or tall sizing or see a tailor to pair down that wider shirt so it both fits you width and length wise.
When looking for coats and jackets, because of your height, finding a coat that hits at the knee is great for you because you have the proportional height to wear it (especially ones with belts) vs. someone of a shorter stature where that type of coat would make them look short/squat/kid-like. For suit jackets, go for a two button coat rather than a three which visually tends to add more length, and if you have an average height/weight body, double breasted numbers are your friends. Avoid a high rise pant, not that they make many of those for guys, but avoid. Find something that hits at your natural waist or a little bit lower, and with a straight leg.
Where to Shop: Good news is a lot of mainstream retailers now offer tall sizing. You may not be able to find it in store, but go to their websites where they offer longer inseams on both shirts and pants. Online stores like www.kingsizedirect.com, https://www.forthefit.com/ , and Asos.com offer a lot of sizing choices for the really tall guy.
The Overweight Guy
Description: You know you're overweight, or maybe even obese. There is no denying it, but people, especially in fashion, tend to ignore your existence as if you don't also need to get dressed to go out or go to work or they think you have no desire to be fashionable or well dressed. Um, you do very much exist, and there is fashion to be had, though you may have to work a bit harder to find it.
Advice: Resist, resist, resist the urge to wear big dumpy shapeless sack-like clothing. When you wear something a couple sizes over your actual size, you give off the impression that there is more bulk below the clothing than actually exists, and seriously, who, man or woman alike, WANTS to look fatter than they actually are. Go for clothing in your size and instead of piling on shapeless sweats, go for fitted structured jackets and pieces made in thicker materials that skim over your bulkiest parts. If you aren't a fan of your size, avoid bold bright patterns and styles. Keep it simple with one or two colors, and look for patterns that aren't horizontal in nature and that create the illusion of being slimmer like a black shirt with white stripe down the center or diagonal prints.
When it comes to your waist, don't do the thing where you allow your pants to ride under your stomach, because the stomach you do have is just going to pool over and do exactly what you don't want it to do which is emphasize that region. Wear your pants at your waist, and if you're still self conscious about it, wear that jacket or a button down that won't hug your frame, but skims it in your actual size.
If your shirt buttons or zippers are pulling, go up a size or two to fit the biggest part of you...and then have it tailored so that you eliminate extra bulk. Other obvious things can be done like wearing darker colors on parts you want to de-emphasize, and rocking vertical as opposed to horizontal stripes to visually give off a smaller look. If you have no neck, open up your collar a bit and or wear things like v-necks to regain some real estate.
Tailoring is your friend, especially when it comes to suits (for any man really). Don't just buy something a couple sizes up, and have it drooping all around you. A great jacket, and pants that actually fit you, can make you look just as amazing as anybody else, and don't you forget it!!!
Where To shop: Try websites like www.kingsizedirect, www.destinationxl.com, and chubstr.com
The Short Guy
Description: If we're talking short for a guy in the US, we're probably talking under 5'7 or 5'6.
If you've reached adulthood, odds are, you are the height you are going to be for the rest of your life and there is absolutely nothing wrong with that, but if it does seem to bother you, there are of course, products called shoe lifts, that are akin to a woman's high heel, that you can add to your shoes or buy your shoes constructed with the lifts in to add height, but without looking somewhat obvious, it will probably only give you about a 2 inch or so lift which if you're already say 5'5 isn't going to make that much of a difference, so give embracing your height, a try.
Visually, however, if you are still thinking about wanting to add the appearance of more height, you want to look for clothing with vertical details like stripes, buttons, patterns, etc. Draw the eye up by wearing monochromatic looks or wearing a bright color up top near your face and open up your shirt a bit or wear v-necks. Avoid long coats, hair, and jackets which can drag you down and make you look like you're wearing your dad's clothes. In general, the slimmer and/or smaller you are, the smaller and slimmer your accessories should be. Thin belts, ties, no chunky jewelry, no big clunky shoes. Fit your size.
The thing about wearing short sleeves and shorts is that they visually chop up the body at the sleeve and the cuff of the short, and if wearing a belt, at the waist. This can actually make you appear shorter than you would if wearing long sleeves and pants because the lines of the two together are nice, long, and continuous. Obviously, you'll probably die in the summer if you attempt this outside of air conditioning, but when wearing shorts, go for a fitted short, straight leg, not one that god forbid has pleats or blooms out in a more a-line fashion.
Lastly, see a tailor and get those pants hemmed, get your pants cut to the correct length, go for trousers with no breaks, have buttons raised to slightly above your navel, and have that bulky jacket or shirt pulled in a bit. The bigger and floppier your clothes are, the more you'll look like a little kid trying on his dad's things. You need to keep things streamlined and fit, and emphasize long clean lines, and keep accessories up top.
Where to Shop: Looking abroad may be a good help for you. Visit the Asian markets in particular, online or in person because average height there is much more akin to your height here which means clothing tends to be cut FOR YOU as opposed to you always having to go to a tailor or hem things yourself. Try online stores like https://www.forthefit.com/ , http://www.petermanningnyc.com/, www.jcrew.com (makes extra small clothing sizes for men)