Also, don't get too busy. Something that I've noticed here is that the people in my squad were excellent at one or two things, but not average in a lot of things. If you love the Physics club, go with it! If you're wanting to get into CAP just to have it on your resume, I wouldn't worry about it. In two years you might be able to get to C/2d Lt, and the leadership helps, but more people are here who weren't a part of that than those who were.
I was in CAP, and it taught me a lot about leadership and whatnot (how to shine shoes, wear uniform, etc.) When you get here, you're on the same playing field. Friends with no prior, preppy or ROTC/CAP experience have just as shiny shoes, just as well made beds. Only advantage? Maybe know what's going on in some of the upperclassmen's heads because "you've 'been' there."
I'm not tell you or anyone not to get involved with ROTC, CAP or join any other clubs. All I'm saying is that it's better to be excellence where you put your time than to be mediocre in a lot of things.
I had student government, CAP, sports and church activities in addition to school. Those took a lot of time, but I did better in those because I had time to seriously commit to them than if I also had car club, chess club, drama club. Get what I'm saying?
I have a friend who starting the beginning of his Senior year to try to make his application way more competitive. School plays, volunteering, leadership (also tried to get into CAP), and we both got the Texas Senatorial nomination. But he didn't get in, and overall, he stretched himself way too thin his senior year if that makes sense.
Now here, you can do anything you want. Just make sure that you're willing to do "anything" doesn't end up hurting you than helping.
But something else is that there are seminars that make your application competative that might only last a week. One big one that I did was Boy's State. It was a great experience, I got Lt Governor, made friends, and helped my resume. But it wasn't frivilous or anything like that.
Once again, not trying to put out your efforts, just warn you against a trap I've seen too many people get caught in. The Academy wants excellence, and you've got about a year to do so. So, be the best you can be and do your stuff well. Don't be scared to try new things. If you can be excellent in everything, more power to you. Just don't hurt yourself in trying to help yourself.