BOWTIES
Always self tie your bowtie because pre-tied bowties are flat and childish. If you cannot tie your own bowtie because of a disability then I understand, but if a physical barrier doesn't exist then you should learn if you intend to be a well dressed man.​​​​​​​
This guide was helpful to me when I learned. I watched a whole movie and practiced until I got it right.
Elevated classic
Elevated Modern
Elevated traditional classic
SHOES
There are three types of shoes you should pair with a tuxedo, regardless of the tuxedo fabric color. 
The first, and my preferred, is a "standard" box-calf (young fine grain) leather whole cut (single piece of leather with only one seam at shoe rear) oxford (fully closed vamp closure as opposed to the Derby closure). Because this is a matte finish oxford some people think it's not elegant enough, despite being a whole cut shoe, in which case I suggest shining the toebox and possibly rear of the shoe either yourself or by a cobbler. This will protect the toe of your shoe from impacts and provide a luster that is synonomous with elegance. Alternatively you can choose to wear a patent leather (shiny piano black) oxford, but from my experience they're much more stiff and you'll probably not wear it with anything but a tuxedo, as opposed to a standard leather shoe that you can wear with a traditional business suit.
If you insist on wearing a whole cut patent leather shoe then I recommend one from Carmina or Tom Ford. Avoid the derby closure unless you have wide feet as the derby system is considered more casual than the oxford closure, and thus odd when paired with a formal tuxedo shoe.​​​​​​​​​​​​​​
Wax shine a calfskin leather shoe for added elegance. Do not apply wax to areas that bend because wax dries hard and will crack into white dust when bent.
Saphir is the best shoe polish that you can use.
Elevated Whole Cut Oxford
This is the pair I own and is my preferred tuxedo shoe because of it's timelessness, comfort, and contemporary last shape. Justin, who sold me the James said "it's soft because it comes from a young animal"
Perfect middle tier Whole Cut Oxford
Same last (shape) as the James. The leather is not as supple as the James, but this is still a top tier tuxedo shoe, and the toebox is so elegantly shaped.
Base whole cut oxford
This is arguably the best base whole cut oxford because it's based on the last from it's parent company, Carmina, that has been creating shoes since 1866. That means you're getting the heritage last at a more entry price point.
Middle tier Black Velvet Slipper
I personally so not like slippers with tuxedos. I believe slippers are only appropriate with a smoking jacket, not a full matching tuxedo, but if you insist then the Crockett & Jones Albert is a great option. It has a beautiful quilted footbed, and although I would absolutely never suggest going barefoot in a formal shoe, if you did at least it'll be in style and comfort. I suggest wearing a no show sock, specifically one from Swole Panda (because they're bamboo and breathable), and I would refrain from wearing calf-high socks with slippers. In addition, I would avoid wearing slippers with black peak lapel tuxedos, and instead try to pair them with a midnight blue shawl lapel tuxedo, or better yet a velvet jacket.
Elevated Patent Leather Oxford
If you insist on wearing a whole cut patent leather shoe then I recommend one from Carmina or Tom Ford. Avoid the derby closure unless you have wide feet as the derby system is considered more casual than the oxford closure, and thus odd when paired with a formal tuxedo shoe.
THE DIFFERENCE BETWEEN THE OXFORD AND DERBY SHOE CLOSURES
THE OXFORD LACE CLOSURE SYSTEM
Closed vamp, straight laced, means a tighter fit and more elegant clean appearance.
THE DERBY LACE CLOSURE SYSTEM
Open vamp, can be cross or straight laced, a looser and more flexible fit designed for wider feet.
POCKET SQUARES
This is a black tie accessories guide. If it was a suit guide then I'd say you don't have to wear a square, but in formal-land you should absolutely wear a pocket square with a black tie outfit. If it's a velvet jacket you can choose a white pocket square with a black trim, if you're wearing an ivory dinner jacket you could opt out from the square, but it usually doesn't hurt to wear one anyway.
Base white pocket square

White pocket square with black trim

Interesting pocket squares