If you are interested in going to graduate school in chemistry or a related scientific discipline, the most important thing you can do besides being successful in your classes is become involved early in undergraduate research. Graduate schools strongly value students who have spent one or more years working on a research project with a faculty member. In addition, this experience gives you a very good idea of what graduate school will be like. Toward the end of your junior year and definitely before you senior year you should take the GRE exam, which most graduate schools require. You should begin applying for graduate schools in the fall of your senior year. Seek advice from department faculty about what graduate schools to which you should apply.