The Common Application provides a place for you to indicate whether or not you will be continuing an activity in college. You might be inclined to select yes, just to show that you are committed to the activity. It is best to only select the activity if you are considering it. There are few things to keep in mind when selecting the activities for future participation. Do not select an activity just because you know that school is searching for it. Do not select basketball for Harvard, if you only have minimal experience with it. However, if you played throughout high school and are still on the fence about whether or not you will play, it would be better to say you will participate.
You should try select one or two activities. This shows that you have thought carefully about what you want to do in college, and have some foresight. Selecting the little checkbox is not all you have to do to show you are planning on continuing the activity in college.. If you think you have something to offer to the activities you plan on continuing, you should contact the head of said activities. You should let them know you are applying and are interested in continuing the activity in college. Some will send you more information about the activity, some will ask you for more information so that they can consider using whatever influence they have to push for you, and others will ignore you until you step foot on campus. In any scenario, it is better to have tried to establish a dialog.