Picking Faction

Where do I get to pick my Faction and how do I get there? Can anybody tell me?

The quests and storyline will lead you to having to choose a particular faction ie- Kurzick or Luxon.

Balthazar is from pvp - random arena etc.

Joining a guild that is either faction allows you to compete in alliance battles through a guild hall which can be another way to pick a faction.

I'd suggest just follow the story and try random arena for some fun/ let off steam etc.