1. Get involved and get out of your comfort zone. High school is a time where you don't have to worry about working or supporting yourself. Use this freedom to do something you never thought you'd do. You also have the benefit of going to a public school, which means you will never get turned away from a team or club. Put yourself out there and try a different activity. I regret trying more things while I had the chance, so this is my plug to not make my mistake.
2. Be nice to everyone. I'm not saying you have to be BFF's with every single person, but it's really not worth your time to make enemies. You will all be gone within 5 years and no one is going to remember who called who a bitch behind their back or who dated who for two weeks sophomore year. It's usually pretty petty and not worth holding onto past graduation. Life will go one and something new and exciting will happen that will be the talk of the hallways.
3. Having a jersey on Football Fridays or a date to every single dance is not the most important thing in the world. You can still dress up cute for games without wearing some benchwarmer's number on your back. You can still have a blast at Winter Formal even if you get all gussied up and go out to eat at some "Fancy" restaurant (aka Applebees) with some of your closest girlfriends. You are a strong independent woman and you don't need a man on your arm to prove it. Plus, without a date you can dance with all the other boys who didn't go with dates. Remember boy math: many adoring men > 1.
4. Study your butt off. High school is not the time of your life, college is. You cannot get into college if you don't get good grades. Therefore, study, turn in your homework, and do well on your schoolwork. Trust me, sacrificing some fun in high school can lead to a lot of fun once you're in college. And no, mom did not tell me to put this part in here. I'm just speaking from experience.
5. Don't worry so much about boys. If you leave the house wearing an outfit that you picked out solely to impress a boy, go change. Yes it is fun to flirt and have flings, but only 12% of high school relationships turn into marriages. The odds are stacked against you. Plus, you have the rest of your life to deal with boy problems. Enjoy your youth and innocence. Stay away from the male humans! I will not be around to disapprove of a boy and I will be the crap out of any guy who hurts my baby sister! Remember, you will have about a hundred or so boys to pick from in high school. In college, you will have thousands. It's hard, I know, but avoiding the male species during high school will make you better off in the end.
I know by now you are tired of this lecture. Just know I do this because I love you. I don't want to see you do the same stupid stuff I did in high school. I won't be around every morning to say how beautiful you are or to make sure your outfit is appropriate (If you don't want Grandma to wear it, you shouldn't either). I won't be able to hold you and cry with you after your first break up. However, I do care about you and want to see you blossom into a beautiful, vibrant, strong young woman the next four years. I don't have many worries that you won't. I'm always a phone call away and promise to never judge any of your decisions. You will be compared to me a lot coming up, but that doesn't mean you aren't your own person. You have a lot of qualities and attributes that I envy, and don't you forget it! Well you are probably super embarrassed and annoyed that I went on this long, but you'll thank me later. Happy Birthday Baby Sister!