Fashion people generally love to dress up for Halloween. After all it is the chance to dress like someone you're not, in fact it is expected. The more outrageous your costume is, usually the more reaction it generates from friends and loved ones. It is the one time of year in which you can be whomever you want.
Personally, I tend to usually procrastinate and become overwhelmed with the endless possibilities. Unless planned way in advance and I mean waaaay in advance....like middle of summer advance, I sadly scramble to put something together.
Funny enough I have never wanted to be someone scary. As a kid I tended to go for the basics like a witch or a ghost. Since college Halloween has always been the perfect excuse to dress slutty..there was the slutty cop, the belly dancer (pretty slutty), the Greek Goddess (sort of slutty) and the German Beer Girl (the sluttiest). Funny enough I don't recall ever feeling comfortable in these costumes, in fact I usually felt super uncomfortable in them, which is not exactly how you want to feel if you want to look sexy.
Therefore, although I am sure you already have your costume picked out this year my advice to you is that whatever costume you choose, whether it's scary or basic or funny or slutty, just make sure you rock it! Don't rock it enough to get by, convince people you are who you're dressed up as.
My best costume EVER (so far) was the time I dressed up as Trinity from the Matrix. I didn't exactly choose it, it just happened to be the last costume at the Halloween store that fit (no joke) and so I bought it and decided to make the best of it. I spray painted my light hair black, wore sunglasses all night (even inside) and funny enough (quite funny to me) introduced myself to EVERYONE as Trinity. I even made my friends call me Trinity that night. It worked! Everyone believed that I was Trinity and people LOVED it. Best reaction I have ever had to a costume and all because I felt comfortable and owned it.
Therefore, it doesn't matter if you dress slutty or even if you look exactly like who you are dressed up as. What is important is that you OWN IT! So get out there and don't be afraid to work it!