You need to be career ready because without some sort of plan you will either end up in a job you dislike, are unprepared for the world of work, or flounder some one job to another. This can be costly.
Depending on how old and whether or not you're still in school, you can begin preparing for a career anytime. If you're still in school take a few minutes to make a list of the hobbies, interests, sports, anything you're passionate about including causes (like saving rescue pups) What are your favorite classes/ clubs and why. Do you tend to get involved in activities with others or watch on the sidelines. Do you like working with your hands trying or building things, do you have a creative side or enjoy doing charity work? These are all things that can help you narrow down the areas that you feel most comfortable in. If you see someone doing a job and it fascinates you, ask to speak with them about how they got where they are, pros, cons etc.
Another thing you need to begin doing is putting together a resume that entails, any work experience you may have such as babysitting, helping at a fundraiser/carwash - anything that shows you're a team player. Also in the resume include any honors/award or recognitions you've received. Know this all sounds tedious but a pattern may emerge that will point you in the direction you are meant to go. For example, you enjoy cooking and creating new dishes but never thought those skills could turn into becoming a Chef. If you're just beginning high school start a resume now, even if only on paper. Keep track of the things you participate in, enjoyed doing.
Lastly, keep a positive attitude. None of this comes easily and in today's crazy world you have to be proactive. GoodLuck.