how did dean nd rory met???

They meet in the "Pilot" episode when Rory was cleaning out her locker from Stars Hollow High to transfer to Chilton. She drops some papers from her box of stuff and when she bends over to pick them up Dean is standing a few feet of way and it surprises her. She makes a movie reference about the way he is quietly standing there which he gets the reference and thats how they start talking.

Here's the scene from the pilot:

rory and dean meet at school at rory old high school