Learn to tell appropriate, funny jokes. Everyone likes to be around someone who makes him or her laugh. Give genuine compliments or thanks for help. Be a good listener. Complain about teachers and homework, parents, brothers, sisters, etc.
Kids like to be around other kids who share the same ideas and problems.
Keep your unique and special talents and qualities. Don't fall into the trap of only doing what others say. Be a leader and let your good ideas be heard. I get so embarrassed when I drop stuff or get lost. Humor is the easiest way to smoother over most embarassing situations.