Try to stay with me now: Allow me to *ahem* clarify for those person's benefit who weren't able to follow along previously. With reference to sneakers and jeans, I meant whilst at work (save for weekends or holidays). That Seinfeld couture of acid-washed jeans, blinding white sneakers, and a bad rugby or monochrome buttondown says "lazy" and "overmatched". Again, this would only apply to work dress (if you work at home or simply never see the light of day from your basement cubicle then I suppose it really doesn't matter if you wear anything at all).
W/r/t to open toe/heel, I meant never to have the two at once...again, at work. This is the classic flip-flop scenario. If a woman wants to wear a mule with a closed toe, fine. If she wants an open toe, there better be a strap around her shapely heel. As for slippers - what you wear in your bedroom is beyond my concern. No doubt Mrs. Eno admires your mesh banana-hammock.
Socks: with jeans, simply match up as best you can - nothing worse than blaring white socks poking out as you cross your leg at your desk. Dark blue jeans? Dark blue socks - $5 at Banana Republic. Oh, and jeans should only be blue. Black is fine if you work in the theatre, otherwise, you belong behind your Dungeon Master screen, rolling twenty-sided dice. Plaid obviously demands a solid. I recommend in that case you first consult the master color of your pant leg - that which your field of plaid rests upon. Failing that, or to be particularly stylish, you choose to match (rather exactly, please) a shade from the plaid. Do not try to match the color of your shoe.
Dockers are evil because they are the cotton sweatpant equivalent of the tennis outfit. Dull but cheap, insipid yet widespread. Worse still, they inspire people to wear non-standard colors. There is nothing wrong with a good cotton khaki, but let's rein in those shades, shall we? Keep to tan an its many varieties. I concur that the khaki can be abused (most often when paired with the blue blazer and light blue shirt), but the khaki can look great rolled at the cuff while at the beach, or neatly pressed and offset with a button-down or sweater.
More still: do away with the grey wools and blue blazer. Yes, it's technically fine, but over-used and wildly abused (nothing looks worse when done badly or when ill-fitted). In winter, I like grey wools, but if I go formal, then it's in a suit. Otherwise, the grey pants look great with just about any shirt/sweater combo you can envision.
Black on black is tricky. I'm of the opinion that such a combo only belongs at a nightclub. God forbid you wear the black suit, black shirt and then say a purple metallic tie. "Just what part of Piscataway are you from then, sir? Oh, you're in the mob? My bad. Please don't whack me."
Please, use those little buttons at or near the points of your collar. They're there for a reason. If no buttons, then look for those plastic collar stays. Can't find them? Get an old credit card or i.d. card and cut to fit inside the collar. Whatever you do, do something. Nothing worse than the curled up collar.
Tie chains? You must be 70 y.o. or attending some function where the tie chain is part of the regalia.
Cuff links - use but do not abuse. If people look and start to chuckle- chuck 'em. Understated size of gold or silver with perhaps a monogram engraved is a good place to start.
Oh, I could go on...