In the past i think we have all struggeled with becoming confident in our selfs and being more outgoing, personally i've had some past problems with being really so i will give you personal tips tht will help you on the journey to becoming who you want to be.
~~-One of the first things you want to do is make eye contact with people, if you don't feel comfortable doing this then you don't have to but it will help you. I wouldn't recommend doing this with someone who you really like! As it will make it uncomfortable. After you engage in eye contact try starting a simple conversation, "Hi", "Hello" , "Hey",etc .
When you first meet people, you should get their time this way you can use it right away.
Just be yourself, don't try to be the popular girl in school who knows everyone.
Become friends with guys, they have less drama and they are easier to talk to and you can just vent to them about your girl problems.
~~Other tips that might help you in becoming outgoing is;
01.) Having outgoing friends, by having outgoing friends you will get to meet new people and try new things.
02.) Be involved. I overcome my shyness by becoming involved in sports(softball to be exact), i didn't know many people on the team and i got to meet new people and got lots of new friends. Get involved in school activites like band, plays, clubs, sports,etc
03.) Smile at People. Smiling at people can make them feel better and that you are genuinely nice. I never had a problem with smiling at people as I've always loved to help people and make friends easily.
04.) Have a sense of humor! Be funny, try making jokes about what you have in common with people and even make inside jokes with your friends. By being funny you will be able to lighten the mood and make people want to be around you