I'm studying Switching Section since I back from Narbik's bootcamp. My study method, which is according to Narbik's recommendation, is Narbik's Workbook 2.0 and follow by DocCD for respective technology/section.
This post is nothing special but it comes to my mind for Open Ended Question Preparation.
"Make sure the native VLAN for an IEEE802.1Q trunk is the same on both ends of the trunk link. If the native VLAN on one end of the trunk is different from native VLAN on the other end, spanning-tree loops might result."