Well...it seems that I opened a big can of...styles and ways of dressing oneself





Now, to be fair; you can wear anything anywhere if you have the "balls", or the sheer audacity, to do so

There are soooo many styles to choose f that your head can spin faster than a dryer on the hot spin cycle! Besides, not knowing what people deal with in real life, I'm not the kind of man to make comments at someone wearing pajama bottoms at Wal-Mart because he/she forgot to buy milk to feed the kids in the morning...some people have difficult life and it's not my place to judge.
As I said before; context is key. Should I wear a neon outfit at a funeral? No; unless the family of the deceased asked for it

Where to begin?
PoopaPapaPalp mentioned a very important aspect of life: personal hygiene and the routines of life that can have an impact on your day...every day.
Sure; you're wearing a good suit, but the Devil is in the details: nails are too long and dirty, shoes are scuffed and have not seen a shoe-polish from the day you've bought them...tie is badly knotted, curled shirt collar...etc. Stand straight, don't hunch, wear deodorant and comb your hair
These are things I'm going to see/check right away. Yes, my background is half Army and half Police and I'm 6'2" and slim...from Brussels, Belgium. (I know; it's a disease, but it's bigger than me

). Being of European education/tradition, might be something strange to some and not to others...we'll see how it all pans out.
The fashion (High Fashion)Industry is like a weather vane; they can change measurements numbers, sizes at will (I will not talk about "Prêt-à-Porter") which is in another Galaxy altogether!
The big "change" in the last 10 years or so are "Vanity Sizing". What was a size 18 has morphed into a size 16 for example. It gives the consumer the feeling/idea that you've suddenly lost weight, which makes you happy...which makes you buy.
Usually, this industry works on a set of "Traditional height" (5'6"), so if you're not; it's going to be difficult to choose clothes that fit.
The "Off-The-Rack" option will be there if you have a trusted tailor that can modify said clothes.
Remember: you have to work with what you have, not with what you don't have! These tips/tricks will be inclusive; people come in a myriad of shape and size and height. This thread will respect and treats our members with decency and civility.

Traditionally, men are lucky to have so many different sizes and fits than women. We have numbers and sizes. Not so much in women's fashion.
Jackets:
Sizes: from XXL to S or a number.
Brands will cut the jacket differently than others. So a "Sport Jacket" from XBrand (fictitious name) will fit you well, while a similar style from another will not. Try your jacket with the shirt, or knit, or combo you'll want to wear with it, in the store.
Different styles: one button, two buttons, three buttons, single breasted, double breasted, etc. Slit (American) or flap(English) or completely closed at the back (Italian).
Some have applied pockets (Blazer), some slit pockets, some have different type of collars and lapels (wide/narrow) some have closed flap at the sleeve and some have the "surgeon's sleeve" (you can unbutton the flap to roll it up your upper arm...more expensive jacket).
Lapels are also something to look for since they come in different designs and shapes.
Usually, the jacket should fit the width of your shoulders. Leave a little space (half an inch) in case you want to wear with the shirt/knit combo...or in case you've gain some weight.
Sleeves should stop above the protruding bone of your wrist. Right hand: the bone is at the right hand side. Vice-Versa for the left one.
Your shirt sleeve should be longer than your jacket's; going a little below that bone.
The jacket should singe your waist to give you a defined silhouette. The length (hem) is also a factor in terms of playing with optical tricks, i.e.: giving the people the illusion that you're taller/slimmer. Choose carefully between a slit, vent or closed back.
By singing your waist, the tailor will have to take some material on both sides of the jacket (side back seam) and doing so might change the look of a slit or a vent (not so much with a closed back). You'll want a straight back (from shoulder to butt) and not a jacket that follows the curvature of your spine or your butt.
The front should also have a straight look. I tend to put the buckle of my belt at the side of my pants (one loop over to the right) to avoid the bulge of it deforming the front of my jacket (that's just me; the crazy Belgian

). Since your tie is over your belt (and belt buckle) nobody sees my trick!
There; I'm sure I've missed some details...they'll be answer with the on-going discussion