First, I only own boxers, so I'll focus my attention there.
Regular boxers or boxer briefs?
While I find the former to be more comfortable, I recognize that they can bunch up - much less likely to happen with boxer briefs. But I just don't like boxer briefs at all and this is kind of about comfort. Or access. Usually I have to pee before an interview and I prefer suspenders ("braces") to belts and the whole operation runs more smoothly with regular boxers.
Fabrics:
Plain cotton: neutral and happy, very versatile.
Flannel: warmer than plain cotton, still very friendly.
Knit: airy and fun, but prone to bunching.
Silk: do not breathe and people who buy silk clothing things (other than neckties) are sickos and/or perverts and should be avoided like lepers, which they might be.
Wear plain colored socks that do not fall down, but stop being ridiculous and take off those things that artificially hold up your socks.
Does the blue or ivory shirt go with the goldish-black tie with some blue or the blackish-blue tie with some gold? Both do! Mix and match! A color-blind man's wardrobe is very much an indispensible asset.
You will not be able to iron your shirt as nicely as the cleaners do, but since the only part anyone will see is the collar (which has collar stays to keep things in line), some of the front (mostly covered by a tie) and cuffs poking out of the jacket sleeves - don't really worry that much about it. Unless you're going to lunch and will be removing your coat - then get the cleaner to do it because you'll screw it all up.
Trim your toenails for that delightful "clean" feeling. Also because my generally laissez-faire attitude to toenail trimming can lend itself to some uncomfortable experiences with the black shoes.
Cold water doesn't dry out your hands as much as hot, but sometimes you need hot water because it can help with sweaty nervous palms. Either way - you should wash your filthy hands.
