Clothing: stuff that suits her body type. Especially cute tops that let me see the shape of her waist and DONT have boobs sticking out (Because I think showing off to everyone is slutty). I have a thing for waists really. Some girls just have a waist that I almost can't resist wrapping my arms around.
Makeup: just a little bit of makeup, nothing over the top. Foundation to cover up any bad acne and very little eyeliner and lipstick. maybe a tiny touch of blush. Her nails should be painted nicely, toenails as well if wearing open toed shoes.
Hair: Change it up every couple of days. I really like girls who can do all sorts of different hair-styles. One day have a pony tail, the next day wear it on your shoulders wavey, then pin it up in a really cute way. I prefer long hair, but I like short hair a lot too. Cute stuff like ribbons, bows and cat-ears are cool too. If you decide to dye it, don't do something completely abnoxious, Bright Blue or Hot Pink hair only looks good in Anime's and for Halloween. Colored Highlights are Awesome though.
Tendencies: Openly shows affection towards me. Laughing and smiling a lot. Running with my playful banter. Talking about common interests. Being Honest with opinions. Humming or singing softly (because If I like you, I'm gonna REALLY like your voice)
Clothing: Clothes that fit well are usually the sexiest but I'd rather see a girl comfortable than in pain in jeans that are too small or something
Hair/makeup: The more natural the better. As far as makeup I feel it is best used to cover up little imperfections and I hate the heavy makeup look. For hair usually sticking to your natural color with length somewhere a little past the shoulders or anything around that is best.
A girl smiling/laughing is attractive. I'd much rather see that than a girl moping around and being depressed. I wouldn't want the laughing to be obnoxious or loud though and not too childish and giggly.
Be genuinely nice and friendly. That means you can't go out and act like that to make yourself more sexy, but actually have to be a caring and pleasant person in your core. I think I can often tell the difference.