Citadel: Party

To properly celebrate shore leave, crew members have suggested throwing a party. Gather party ingredients, and invite friends over.

Acquisition
After retaking the Normandy, Joker suggests throwing a party.

Preparation
After Joker suggests throwing a party, you will have to go the kiosk at the bar on the second floor of the Black Star Casino and purchase Party Provisions for 100 (90 if both discount bonuses were chosen at the Intel Terminal) credits. Afterwards, return to the office in the Apartment and send out invitations using the private terminal. All Mass Effect 3 squad members, Steve Cortez, and Samantha Traynor are automatically invited, but you can invite any surviving squad mate from the first two games that has completed their full Mass Effect 3 story arc. For example, Grunt will be available upon completion of the Attican Traverse: Krogan Team mission, but Miranda Lawson will not be available until after Priority: Horizon. Wrex will be available, as he was for the DLC's campaign missions, as long as he survived the events of Virmire in Mass Effect 1 and the  genophage was cured. All appearances are contigent on their survival in their respective missions, which means that certain squad members will not appear under any circumstance. Your guest-list will have inluence on the group arrangements; so for example if neither Samara nor Wrex, Zaeed and Tali are present (due to being killed on Virmire, not enough Mission progress or not being invited) there will only be 2 groups (Energetic Theme) and Javik will be sitting next to Samantha Traynor instead of being upstairs and talking to the "warriors"; Grunt, Zaeed Massani and Urdnot Wrex (Grunt was with James Vega and the Group sitting at the couch-table)

So it's highly recommended to first complete all missions, to get the most out of this party.

Choose a party theme
When the invites go out, Glyph will ask the Commander what type of party should be held: Quiet or Energetic. These choices will affect the initial dialogue in the first part of the party but not the group arrangements.

Second theme
After speaking to each group, Shepard can speak to Glyph a second time and either keep the theme going or change to the other. The second theme can be considered a continuation of the first, but it is in no way dependent on the previous choice, it has the exact same character positions, group arrangements, and resulting dialogue. For example, in the Quiet Party's second half, Kaidan will be sitting with Joker and Traynor, but in the Energetic Party's second half he will be standing with Liara (and Jacob Taylor if available) talking to James Vega.

Wrap up
After talking to Glyph a third time, you can choose to begin the final phase of the party, or send Glyph to address an issue dependent on the theme. In the Quiet Theme, it can be sent to assist Traynor with drinks, and in the Energetic Theme it can be sent to diffuse a standoff between its boss and  Muscles. This has very little bearing on the rest of the night, with the Quiet Theme defaulting a poker game between Liara and James, with Javik spectating, and the Energetic Theme defaulting to dancing.

After speaking to all groups and listening to as much dialogue as you wish, approach the couch to assemble the team for a Group Photo.

Aftermath
Shepard wakes up, potentially with their love interest in their arms, and assesses the aftermath. If he survived Mass Effect 2 up to the completion of the genophage arc in Mass Effect 3, a datapad containing recordings from Mordin Solus will be available on the floor. Most characters' dialogues are no different regardless of the second theme, while others are more sobered up or hung over.

After exiting the apartment, Shepard signals the Rapid Transit to return everyone to Docking Bay D24, reminding them that the war is still going on. The Mass Effect 3 crew gathers at the observation post looking at the Normandy as the DLC comes to a close.