[edit] Steps

Have a bath and buy a shower gel that smells really nice (some nice shower gels include Soap & Glory Clean or Me and BeneFit Gettin' Steamy) Although the smell might fade, you'll still feel nice.
Wash your hair with a nice shampoo, if you don't use conditioner find one that smells nice, like Schwartzpoft Coconut & Yoghurt, or Herbal Essences. Make sure you find a shampoo that suits your hair. Herbal Essences conditioner is really good, it smells nice and makes your hair feel moisturised.
Put a face pack on! Face packs only cost about 99p. Leave it on for about 10-15 minutes or how long the packets says. If you can't afford one, use some stuff from home like natural yoghurt or honey, as they both make your skin feel soft and clean out pores in your skin. If you want to fee relaxed, slice some cucumber and put it on your face!
Use a nice smelling body lotion when you get out of the bath! Avon Naturals do some really nice ones, or if you buy a perfume, a body lotion with the same smell usually comes with it, so use it then!
If you want to put on fake tan, exfoliate before you put it on! Get rid of all the dead skin. To exfoliate properly, use an exfoliating glove or scrunch, and make sure you focus on think areas of your skin, like elbows and knees, as the fake tan could turn really dark.
Nails - never bite them. If you can't stop buy some nail varnish that tastes disgusting. If your nails are really weak buy some strengthening varnish and Avon Grow Potion is really good too or Sally Hansen.
For about 5 minutes soak your hands in warm soapy water, then pat them dry. if you rub them it can damage your skin. After push down your cuticles or clip them off with cuticle clippers, or apply some cuticle cream. Afterwards, put some nice hand cream on.
Always put heat protection on before you blow dry or straighten your hair. If you have thick frizzy hair, point the hairdryer downwards so the hair cuticles will lie flat. Seperate your hair when you straighten it so it's easier.
In the morning have a shower again, because overnight you sweat and your skin is moist. This will also wake you up if you feel tired and will make you feel fresh. If your shower handle doesn't move around, put a shower cap on.
Straighten your hair again if it's gone frizzy or flyaway.
Wash your face with a cleanser. Some good ones are Clean & Clear (especially if you have spots), No7, or Clinique.
Put moisturiser on your face. It will help spread your foundation more.
If you have primer, put that on too. A good one is BeneFit "That Gal".
Put foundation on, then bronzer so you don't look pale.
If you have short eyelashes, make sure you put mascara on! Maybelline Great Lash is good.
Put some vasline or Nivea on your lips to make them look soft.
Make sure you wear deodorant!
Put some nice perfume on, so you will feel attractive inside and out.
If your school allows jewellery, try a silver beaded bracelet or a nice big jewel diamond ring. A cute silver necklace would also work.
If you have long hair, put some accessories in. Plaited headbands are good (as long as it's the same shade as your hair), or if you haven't got one, do it yourself. Use hairspray to keep it in place.
School bag: Hand bags are good, don't use a rucksack if you don't want to look geeky. Most girls get their bags from Primark or River Island.
If you wear glasses get some contacts or get some NICE ones! Fashionable ones like Gok Wan, Chanel, ect.
Shoes: black ballet pumps are good. Don't wear clumpy shoes. Black plimsolls are good also.
Wear a bra that's nice, colourful and it fits properly.
Get some confidence! Try and get some friends and socialise more.
Don't copy anyone at school.
SMILE! It makes you look prettier.