Vincent Tinto (1993) identifies three major sources of student departure: academic difficulties, the inability of individuals to resolve their educational and occupational goals, and their failure to become or remain incorporated in the intellectual and social life of the institution. Tinto's "Model of Institutional Departure" states that, to persist, students need integration into formal (academic performance) and informal (faculty/staff interactions) academic systems and formal (extracurricular activities) and informal (peer-group interactions) social systems.
Vincent Tinto's home page contains several good articles on student retention.
Tinto's (1993) Dimensions of Institutional Action
I. Defining "Dropout" from Higher Education
A) Dropout as Individual and Institutional Failure
B) Educational Mission
II. The Principles of Effective Retention
A) Institutional Commitment to Students
B) Educational Commitment
C) Social and Intellectual Community
III. The Principles of Effective Implementation
A) Institutions should provide resources for program development and incentives for program participation that reach out to faculty and staff alike.
B) Institutions should commit themselves to a long-term process of program development.
C) Institutions should place ownership for institutional change in the hands of those across the campus who have to implement that change.
D) Institutional actions should be coordinated in a collaborative fashion to insure a systematic, campuswide approach to student retention.
E) Institutions should act to insure that faculty and staff possess the skills needed to assist and educate their students.
F) Institutions should frontload their efforts on behalf of student retention.
G) Institutions and programs should continually assess their actions with an eye toward improvement.
Stages of retention
Recruitment and Admission to College
Orientation: Bridging the Gap to College
Pre-entry Assessment and Placement: Identifying Student Needs
The First Year: Making the Transition to College
Types of institutional actions to improve student retention
Early contact and community building
Academic involvement and support
Monitoring and early warning
Counseling and advising
Effective student retention programs: