Accepting an offer. Once you have decided that a program is right for you, call them to accept their offer and send them a written acceptance. Such predatory behaviour is frowned upon by the scientific community and will not give you the reputation you wish. Further Reading Overall, this is just a primer on applying and getting accepted into graduate school. Seek out additional advice from professors, graduate students, and advisors.
Different disciplines have different criteria.
Some modest advice for graduate students. Huey, R.B. 1987. These two articles offer a pithy and provocative exchange on how to be a successful graduate student. They each offer humorous and sage, if not somewhat contrasting, advice. They should be read by all incoming graduate students.