CK2 Wiki ist gut

http://www.ckiiwiki.com/Crusader_Kings_II_Wiki

Following this Let's Play also made me learn a lot: http://lparchive.org/Crusader-Kings-2/

I don't think you can follow it exactly since there's been a million patches and expansions, but you can still follow it pretty well if you want to learn stuff.

As for taking over lands, you can fabricate claims, pull someone into your court that has a claim on that place and press it, fiddle with the marriages and stuff to get your kids as heirs to the place... There's tonnes of ways.