In America, the most common wedding attire for a groom is either a lounge suit or a tuxedo.

The Jacket
If you decide to get married in a tuxedo, the most flattering and traditional choice is to select a 1 button jacket with a peak lapel. The facings (lapels) should be in silk, but in most cases, satin will also be suitable.
Tuxes can come in 2, 3 or even 4 button form, but on the whole, they look far too much like suits. The same can be said about notch-lapels; if you are going to wear a tux, then do it right. Peak lapels are the ones that point upwards, like the peaks of mountains.

The Trousers
Trouser for a tuxedo should be in a fabric that matches the jacket. When you see people in a green jacket and black trousers, they are actually wearing a smoking jacket, not a tux. Trousers should have a stripe of material down the outside of each leg made from the same stuff that your lapel is made from –be it silk or satin.

Accessories
The Tie should always be a bow-tie. Although many Hollywood stars like to wear neckties or cravats, they should be largely ignored. Unless you are arriving in a helicopter and have a few superstars in attendance, just keep it simple. A black bowtie made from satin or barathea (a matte type of silk) that is self-tie. Resist the clip on! Taking that extra minute or so to tie a bowtie by hand makes all the difference and helps retains some personality in the knot.

The Pocket Square
It should be simple white to match the shirt. Straight line fold, triangles, and multiple points are all acceptable. Think James Bond.

Cufflinks and Studs
Gold, Black, Silver, Onyx. Anything you like, just make sure that they match each other and your watch. Mixing metals can be tricky and is generally best avoided. Having said that, don’t think that you can’t wear your grandfather’s gold war-watch because your wedding band is in platinum. When it comes to weddings, items of sentimental value trump the rules every time.

Shoes
Shoes should be black patent lace-ups or if you want a pair you can use every day afterward then pick up a wholecut or cap-toe in black from a decent maker. Remember to wear them a few times before the big day, nothing is worse than walking around with blisters!

SF member Newcomer via the Official Wedding Attire thread.

There are two ways in which you can approach choosing a suit for your wedding: pick a cloth that is very different from something you wear at the office, so that you don’t feel like you’re going to work, OR pick a suit that you can wear many hundreds of times after you get married, in order to be financially prudent.
Only you can make that kind of decision, but on the whole, there are some guidelines:
Pick sensible colors. While you may love the look of the brown suit today, how will it look when you show the kids your wedding photos? Greys, Navy, and Charcoals are going to stand the test of time better than that sky-blue velvet number you had your heart on.
Two button suits are most proportionate on gentlemen under 6 foot in height. Once you hit the 6ft mark, you can use the 2 button suit to make you appear slimmer and taller, or a 3 button to bring you back into proportion. Generally, a big, tall man in a 3 button suit, looks similar to a normal man in a 2 button suit.
Shoes can be black or brown, but make sure that they are highly polished and worn a few times before the big day. I cannot overstate the importance of breaking in your shoes before you want them used.

SF member and contributor Mossrockss via the Official Wedding Attire thread.

Rule one is always wear a suit. While some guests may turn up in a polo shirt and khakis, you can always ditch your tie for a bit of James Bond flair. Any outfit can be made more casual, but you can’t magic up a tie when you’re the one who’s underdressed.
Blue, Grey, and Brown are all acceptable. Two-button without a waistcoat is more modern, but stepping up to a three-piece can be a nice way to formalize the affair.
Never wear a black suit. Black is a funeral color and most definitely not welcome at weddings.
Ties and pocket squares should complement each other and also complement your date’s outfit, or if you would rather pick out a color of the wedding theme this is permitted as well. Shirts should be light blue, pink or white. Firstly this makes everyone look a little happier by using high-key colors, but also because weddings often mean standing around in the sun or in hot rooms. Sweat patches don’t show of light colors but spread heavily on dark.
Shoes should be black unless you are wearing a very light color of suit, in which case tan may be acceptable.

When it comes to wedding attire, English grooms have the choice of wearing a morning suit (most formal) or a lounge suit.

The morning suit is the most formal attire in use for weddings in the UK and Europe, and even now only represents a very small minority of cases. If Your invitation states “Morning Dress” or some variation thereof then you should consider a suit to a last resort.

The Coat
Morning coats are scarce in the UK so you are limited to Bespoke or a few OTR stores. The coat should be charcoal and made from wool where ever possible. If you are renting then this may not be possible, but do your best.

The Trousers
The trousers of a morning suit should be black with charcoal or chalk stripes known as “cashmere stripes”. This is one of the rare occasions on which matching the trousers to the cloth of the coat is considered wrong. There should be a distinct difference. The cut can be slightly fuller than your normal “slim” trousers; there has never been such a thing as a slim-fit morning suit.

Accessories
The tie should be a satin in pastel colors; pink blue and peach are popular choices. Handkerchiefs can co-ordinate or consider a white linen version if you prefer a more classic look.
Shirts should be white. I would choose a poplin, although still is nicer to touch, it is also thicker and therefore warmer. A morning coat stays closed at all times so you might get a little warm.

Cufflinks and Studs
Gold, Black, Silver, Onyx. Anything you like, just make sure that they match each other and your watch. Mixing metals can be tricky and is generally best avoided. Having said that, don’t think that you can’t wear your grandfather’s gold war-watch because your wedding band is in platinum. When it comes to weddings, items of sentimental value trump the rules every time.

Shoes
They should always be black and as plain as you can find. Do I need to say it again? Wear them at least three times before the big day, blisters aren’t cool.

**Note**  This is section is the same as the American version. Reading it twice will be boring.

There are two ways in which you can approach choosing a suit for your wedding: pick a cloth that is very different from something you wear at the office, so that you don’t feel like you’re going to work, OR pick a suit that you can wear many hundreds of times after you get married, in order to be financially prudent.
Only you can make that kind of decision, but on the whole, there are some guidelines:
Pick sensible colors. While you may love the look of the brown suit today, how will it look when you show the kids your wedding photos? Greys, Navy, and Charcoals are going to stand the test of time better than that sky-blue velvet number you had your heart on.
Two-button suits are most proportionate on gentlemen under 6 foot in height. Once you hit the 6ft mark, you can use the 2 button suit to make you appear slimmer and taller, or a 3 button to bring you back into proportion. Generally, a big, tall man in a 3 button suit, looks similar to a normal man in a 2 button suit.
Shoes can be black or brown, but make sure that they are highly polished and worn a few times before the big day. I cannot overstate the importance of breaking in your shoes before you want them used.

If you’d like to discuss the state of black tie, join the conversation on this thread on Styleforum.

If you’d like suggestions and tips regarding your wedding outfit, you can visit the Official Wedding Attire thread.

This article is an edited and revamped version of an article originally published on September 16, 2011, on Styleforum.net by the user Blackhood.