Establishing a relationship on the phone is an art and requites good interpersonal skills. However, the reward for of a good phone call may save you months of research time. Support engineers will often provide pros and cons of their product over the phone that are not contained in the company literature.
Some Tips Are:
Review material on the web so you sound knowledgeable.
Ask to speak to an application engineer (otherwise you will be directed by default to sales).
Introduce yourself as a University of California at San Diego Engineering Student working on an Industry or Research Project (whichever is more appropriate).
Get pricing and availability on all parts in question (ask if they have samples or educational discounts).
Ask about pros and cons of various options. Ask about strength of the company compared to their competitors.
Always get the name, phone number, and email addresses of the person you spoke to.