Making yourself pretty isn't always about making the "outside" look pretty.
When you are a good person (someone who is kind, does the right thing, is understanding, and is easy to talk to) people will think of you as pretty on the outside as well.
Just be yourself.
It also depends on personal taste weather or not someone is pretty.
Some people think tan skin is pretty, some think pale skin is more beautiful.
some like really skinny girls, and some prefer girls a little more curvy etc. Everybody has different taste.
Also, when you look in the mirror think about the good traits you have - I have really good skin, I love my eyes - that sort of thing.
#1 Being pretty, people ask many questions such as, how should I put my makeup on for a date. Things like that. If you think about it. No one in the world is perfect and each person in the world has something very pretty about themselves, legs, eyes, hair, face, etc. So one day just look at yourself in the mirror and say, "Yes I like that about myself." And if anyone ever says something about themselves being "perfect" and boasting about it, just forget it because they must be really "dumb" because everyone knows no one is perfect.
#2 Number two. If you have a good personality and are kind and generous then people will know you as a good and very friendly person then they will suddenly realise you are not only beautiful on the inside but on the outside too! Most girl's self esteem is brought down by other people telling them they aren't good enough, pretty enough, or skinny enough. The key is, don't listen to what other people think, no other opinions about you matter except yours! Be true to yourself and ignore all the rude comments people tell you, remember you control what you think of yourself and what you believe, nobody else.