It's worth noting that there are BIG SPOILERS for Mass Effect 3 on this page. Read with caution! Your first actual Romance opportunity occurs after Priority: Citadel II. Talk to Diana in her makeshift ...
Players of any kind won't be able to Lock In a Romance with Liara until you meet with her in the Presidium Commons after Priority: Citadel II. Picking "Or more than friends..." will Lock In the ...