The regular application process for veterinary school begins in a given summer for matriculation into veterinary school about 14 months later the following September. The central application for applying to veterinary school is VMCAS (Veterinary Medical College Application Service) and students will submit it by September, selecting the vet schools to which they want it sent. The VMCAS website has lots of helpful information including, among other things, the prerequisites for each school. They do vary somewhat so it is important to check before applying.
The two other components of the application process are the GRE and the letters of recommendation. The GRE is a general aptitude test and is required by most veterinary schools. It is administered very frequently throughout the year and you can see your results immediately. Most applicants take their GREs in the summer prior to submitting their VMCAS.
VMCAS does not accept a committee packet and so prevet students no longer register with the HPRC. Applicants solicit individual letters of recommendation. It is important that you have at least one academic letter – from a faculty member who has taught you in the sciences. Beyond that you should have at least one letter from a veterinarian, and perhaps another from some other animal-related experience you have had.
Many veterinary schools do not interview. The Cummings School does interview. Typically, decisions will come out in winter and early spring.