A:Answer 1. Make sure CPU goes with Motherboard. Both need to be of the same "socket". (ie. LGA1200)
2. If it's the Graphics Card, just make sure the "interface" matches the "interface" you have on your motherboard. (ie. PCI Express 3.0)
You are basically just matching all components to the motherboard. So when you are picking out parts, having a list of your MB specs will help you match everything up.