Realize that you must hold a Ph.D. in your field to even apply to be a tenured professor at a university or four-year college. To obtain a Ph.D., you will have to study for a minimum of six to eight years beyond the bachelor's degree. Decide if you want to make that commitment.
Maintain a high grade point average so that you can receive your bachelor's degree with honors and be admitted to the graduate school of your choice for your master's degree.
Consult your counselor for the best academic route to take toward obtaining a Ph.D. and any teaching credentials you might need. You should know where you would like to obtain the Ph.D. so that you can take all necessary prerequisite courses.
Complete the master's degree, keeping your writing skills sharp and your grade point average high so that you will be admitted into the doctoral degree program of your choice. Your Ph.D. dissertation will take about three years to complete; its quality will determine if you will be considered seriously as a possible full-time professor.
Apply for a full-time university teaching position after you have your Ph.D., but not until after you also have some published writings of high quality. You'll also need to have some teaching experience as a part-time or assistant professor.
Understand that if you are lucky enough to be accepted to a tenure track, there will be a mandatory seven-year trial period before you receive tenure. After those seven years, you may be asked to leave. To prevent that from happening, devote your time to improving the quality of your teaching and your publications, since they are both critical to your being approved for the permanent position.