Hi Honeybee!
In my sorority, and all the chapters on my campus...Big/Lil Week is known as Mystery Week. The week before you tell your Pledge Mom some names of girls that you'd like to be your big, then she matches up your pledge class.
During Mystery Week YOU get presents from your big every day. But you don't know who she is yet. With each present we leave a note with a clue. But we don't always leave truthful clues. :P I can't tell you how much fun it is to see your lil grilling people trying to figure out who you are.
Sometimes bigs will even team up to completely throw off their lils. We'll write each others notes so handwriting doesn't give it away. Sometimes we'll get special presents for the other lil so that they get completely confused!
The week ends with Revealing. You finally find out who she is!! If you like a small present wouldn't be a horrible thing. But it's certainly not required. Flowers are cool, that's what I gave my big. She was shocked!