What to ask when requesting info. about a program?

[LadyMactans]

I'm trying to narrow down my choices for grad school and I want to contact them for information, but I'm really not sure what I should be asking, or even who I should contact. I'm interested in entomology, specifically medical entomology or entomology with an emphasis on vector borne diseases. Although I'm not positive that's what I want to focus on, I'm leaning very far toward that, and I would like to find an entomology program that has opportunities in that area.

That said, should I be emailing the head of the entomology departments at these schools or should I be contacting whatever faculty member is doing research/teaching classes on medical entomology or parasitology? Or should I contact both?

Then, when I do contact whomever I should be contacting, what do I say?? What should I be asking? What should I be telling them? Should it be really casual or formal? Should I be trying to sell myself, or just save that for if I actually decide to apply?

Any information you can give me would be appreciated. Thank you.