Liara T'Soni is one of three romance options available in Mass Effect 1, and can be courted by both a male and female Shepard. She is also a romance option in the Shadow Broker DLC for Mass Effect 2, and in Mass Effect 3. Starting a relationship with her in the first game can lead to a complete arc with her in Mass Effect: Legendary Edition.
How to Romance Liara in Mass Effect 1
The first step in romancing Liara is to locate Liara first in Mass Effect 1, then travel to Feros and Noveria after recruiting her. This gives Shepard more opportunities to talk with her and establish a romantic relationship.
Go to the back of the Medbay to Liara's office to start the first conversation with her and be sure to pick only neutral or Paragon dialogue options in Mass Effect. Romancing Liara isn't too difficult, but players can lock themselves out of the romance if they consistently pick Renegade options while speaking with her.
After completing Feros or Noveria in Mass Effect: Legendary Edition, talk to Liara again and ask to know more about her. Liara will say that there is something compelling about Shepard. If some flirting has happened with either Kaidan or Ashley, Liara will then mention this. Choose "It's not serious," and then "I am attracted to you" to start a romance with Liara instead.
After completing both Feros and Noveria, Shepard will be confronted by Liara and Kaidan/Ashley if players have tried to romance them both. They will force Shepard to choose between them, so make sure to choose Liara unless wanting to romance Kaidan or Ashley in Mass Effect 1 instead.
Once the confrontation has been dealt with, or after talking with the council if players have not been romancing two companions, head to Liara's quarters again. Remember to choose Paragon or neutral dialogue choices to comfort Liara. Players get the opportunity to talk with Liara again after completing Virmire and choosing to save Ashley or Kaidan, but only about Saren.
The next significant romance opportunity with Liara occurs when the Normandy is grounded at the Citadel. If players picked the "I am attracted to you" option previously, and choose Liara in the optional confrontation, she will appear in a cutscene with Shepard on the Normandy. Be as nice as possible to her here, and the conversation will lead to Shepard and Liara almost kissing.
How to Get Romance Scene With Liara
The conclusion to the romance with Liara occurs on the way to the final planet, Ilos. She will come to Shepard's quarters and initiate a romantic encounter. Choose the Paragon or neutral dialogue options to see this scene, or choose the Renegade choices in Mass Effect to skip it.
Skipping the romance scene will still count toward the Paramour Trophy/Achievement, and Liara will be locked in as Shepard's previous romance option either way while playing Mass Effect 2 and 3.
Mass Effect: Legendary Edition is out now for PC, PS4, and Xbox One.