All health professional schools encourage, and many require, exposure to a clinical environment.
Working in a hospital, clinic, physician's/dentist's/veterinarian's office is helpful in confirming your career decision and may result in a strong letter of recommendation to be used in the application process. Note: Vet and Physical Therapy programs require clinical hours.
Scientific research, although not required by most programs, is highly recommended. Plan to spend a summer doing research either on or off campus. Doing a senior research project is also highly recommended. Letters of evaluation from research supervisors are highly valued in the application process.