Mass Effect - Uncharted
XP and Advancement
Each player should choose an Advancement Trigger from the Career they wish to advance (i.e. buy a new skill from). As the game is played, any time ANY character triggers ANY of the group's Advancement Triggers, ALL characters mark 1 XP. An Advancement Trigger may only be activated once per game session, so the maximum amount of XP all characters can receive in a given session is equal to the number of characters in play.
Once you've marked a number of XP equal to the total number of Skills your character possesses, you advance. Choose a new skill from the Career you advanced, cross off the Advancement Trigger and choose a new Advancement Trigger from the Career you wish to advance next.
Your Species advantage is not a "Skill", but your starting Origin skill and three Career skills are. As game play begins, you'll need 4 XP to reach your first advance.