In order to increase retention, the Admissions team should have extensive knowledge on the programs offfered by the school. They also need to be aware of the acceptance requirements of the school and be honest with potential students to find the best fit into the program.
We have grade requirements for certian programs and if a potential student does not think he will meet them, I discuss the other options available and explore why that program is what he wants.
I have found in my institution that many students were unhappy once they started due to what they considered misleading information from admissions.
We have since started making sure that students know requirements and additonal classes up front and continue to discuss it in follow-up calls so that it is not forgotton.