Just like the rest of us teenagers need to be able to anticipate the next step in theirs lives if they are expected to be prepared.
Avoid changing plans too quickly without giving your teenager time to shift gears. Help them use their agenda, day planner to other organizer to keep track of their upcoming activities, obligations and events. If you have to change/make new family plans, try and give them warning and give them the courtesy of asking what impact these changes/plans will have on their existing schedule.
This approach will assist your teen in learning to anticipate, plan and be prepare for whatever is coming down the pipe.