"This is a costume, please compliment me on it. Thank you."
If you dress in such a manner that I can't tell the difference between your normal appearance and a costume, do not act offended when I fail to notice on Halloween.
If you normally wear makeup in unnatural colors that looks like somebody applied it to you with a paint-roller or an industrial caulking gun, if you normally decorate your face so that it looks like the south end of a northbound peacock, if your standard makeup scheme can best be defined as "David Bowman's psychedelic passage through the Star Gate Monolith from 2001: A Space Odyssey" then don't be surprised when I don't notice that your Halloween costume is a mime, Bozo the Clown, Nancy Grace, The Joker from Batman, or a Japanese kabuki girl.
If you normally choose your wardrobe from the Salvation Army dumpster and your Halloween costume is a 60's go-go dancer, a homeless person, a Lehman Brothers investment fund manager, or Kurt Cobain, there's a pretty good chance I won't notice even if you pointedly ask me what I think of your outfit. The best you can hope for is that I'll say something noncommittal like, "It looks good on you."
If you wear camo pants or your dad's old Vietnam Army jacket every damned day of the year and your Halloween costume is a deer hunter, the Deer Hunter, The Master Chief, or a member of the Michigan Militia, well, I'm probably not going to notice just because you added a camo bandanna tied around your forehead and I'll probably be giving you a wide berth anyway.
If your face is pierced through every conceivable fold, flap, lobe, brow, lip, nostril, cheek, chin, and tongue and you've got more stainless steel embedded in your head than a kitchen supply store, don't be surprised when I don't notice that your Halloween costume is a blender, motherboard, cell phone tower, doberman pincher, The Terminator, or Dick Cheney's mechanical heart.
If you are an emo kid and your costume is Dark Matter, Darth Vader, Johnny Cash, Bono, a black hole, black body radiation, the Labrea Tar Pits, the personification of self-pitying angst, or Dick Cheney's black mechanical heart there's a pretty good chance I'll just laugh mockingly at you in my usual fashion unless you either smile or wear something pink, yellow, or generally uncorpse like. Also, try taking a shower.
If you are covered from head to toe in skull and spiderweb tattoes and your costume is a Hell's Angel, a member of the Aryan Nation, or a Folsom Penetentry Alumni out on parole, well, you just stay on your side of the room and I'll stay on mine. OK?
If you are a chimpanzee, bonobo, baboon, Bobo the Monkey Boy, or any other non-human member of the hominids and your costume is George W. Bush... dude, seriously, don't. It's demeaning to your species and it's too easy.
The following costumes are absolutely garenteed to make me kick your ass at least once on All Hallow's Eve: Osama Bin Laden in a 7-11 uniform, Sarah Palin complete with annoying faux Minny-sota accent oh yeh, Tina Fey costume under Sarah Palin costume complete with annoying faux Minny-sota accent oh yeh, a Texan, Sponge Bob Squarepants, Dick Cheney's black mechanical heart, Ted Stevens with his hand out, an Ewok, PeeWee Herman, a Postal Employee, or a Pirate costume complete with large belt-buckle mounted steering wheel so that when people ask about it you can respond with "Argh! It's drivin' me nuts!"
Thank you and please don't TP my house.