(a) the shoes
(b) the hair
(c) the outfit
Usually in that order.
For example..... If I saw a guy walk into Office in seriously baggy jeans with a chain hanging, a black "rock" t-shirt and some ugly black bulky trainers, I'd think "no" instantly. Add a ponytail, a shaved head (although I can sometimes find a loop-hole in this rule for certain guys) and some dodgy beaded man-jewelery and I'm screaming "hell no".
Swap this for Vans, chino trousers, checked shirt and a body warmer and you, my boy, are onto a winner. Feel free to swap any of these for Toms, Nike blazers, anything All Saints, drop crotch jeans, skinny coloured jeans, bobble hats, denim shirts, chunky knit cardigans or jumpers, and you will also trigger the "yes please" reaction in my head.
(Small selection of some of my fave's).
Clearly this is the casual side of life. Throw in a suit jacket or a blazer, some brogues and a skinny tie for an evening on the town and you're bound to look sound.
Of course, like I said, there are exceptions, and some men in drop crotch skinny ankle jeans with Toms and an All Saints t-shirt just should not have bothered.
Dress to suit yourselves boys.
Oh and finally....the hair. This is only a personal opinion, because I know most girls have very different opinions on this, but:
keep it short
keep it neat
feel free to shave it at the back and sides
don't overdue the gel/wax
if you have curly hair, keep it curly. put the straighteners down
no streaks/highlights/drastic colour changes to fool us you're not ginger. your eyebrows give it away
and for the love of god, don't try and copy justin bieber
Take note :)