Noob mulitplayer Questions, how it works ect

Hey guys I've never played online with other people on CK2 before, I have like 400 hours playing time so not a noob in that respect. So yeh I tried to join someones game earlier but wasnt working due to my noobiness and lack of understanding. This is great game and I would love to get into playing some multiplayer. I just dont know what im doing :(

1. Do you guys often host games? 2. How can I join them? 3. What CK2 beta and AGOT mod do I need to have enabled? 4. Expect more questions if you answer the first 3 :)