http://www.greekchat.com/gcforums/sh...ad.php?t=54403
Start there. It has stuff about rec letters. As for knowing someone... I'd say you wouldn't have to. I joined a sorority where I didn't know any one, instead of the two that I did. That was my campus.
Read the rest of the threads. There are certain threads near the top of the recruitment forum that are called stickies (like the link above) that will help answer all of your questions. Now as for your school. I have no idea what SMU is or where it is. Also, since it is your first year at your college, it is a better idea to not be set on any certain sorority. Each chapter is different on every campus. Chances are that other GCers are unfamiliar with your campus.