i've tried a few things in the past few months,and people noticed lol
1) plucking your eyebrows. people notice this so much.
2) highlights or a new hair colour, if you've got dark hair, go lighter etc, people notice!
3) different hair style. it could be a side parting or a centre parting or wearing it up or down.
4) if you normally wear skirts, wear jeans or vice versa etc.
5) add a splash of colour to whatever you wear. so if you're wearing jeans or something, use a yellow coloured scarf as a belt.
6) if you're a comfortable type person when it comes to clothes, if only once, wear a pair of heels (they don't have to be sky high, but it'll work)
7) tone up or lose weight or become healthy
8) make up.
9) use accessories - alice bands, bracelets, necklaces etc
10) if your hair is striaght, curl it or vice versa.
11) paint your nails a nice cheerful colour.
12) stand straight. you'll look better than if you normally slouch.
13) wear nice underwear, when you feel good underneath, it shows.