Find some real friends, don't make some huge effort to have a shit ton of "friends" and be Mr. Popular, it just makes everything harder. If you have a group of 5-10 people who you know have your back you are in very good shape. I would say JROTC helped me in that department, doing stuff with them helped me meet people and get some really good friends in every grade, which can be a big boost for your class performance since they can tell you what to expect from teachers.
You should also make an effort to be polite with people, even if you do not know them. People saying stupid shit is one of the big things that starts fights in high school, you don't want that. It also makes people more inclined to be nice to you. Thats what I am doing and I never got into anything until I broke the rule.
Try to get along with your teachers as well. If your teacher hates you it will only make getting a good grade even harder. I know from experience that ones that hate you do not have much problem fucking you over. If your school is anything like mine, Honors teachers are massive pricks.
You should also remember to work hard in class, you are in school to learn, not jerk around. Though I do recommence that you take some time in your day to chill out some, if you try to work yourself to death you will burn out and go down hill.
Recap,
1. Get some good friends, joining a club or doing sports helps.
2. Don't be an asshole, or someone will rip you a new one.
3. Be nice to teachers, they give grades.
4. Work hard, but don't kill yourself.
EDIT: Also, another important note, do not single yourself out, that invites unwanted attention.