Here, the captain can engage in administrative work with all relevant office equipment at hand without interfering with bridge operations. In addition, this room is usually the preferred place where the captain can hold private discussions and/or receive classified communications.
The set for Archer's ready room was intentionally built to be cramped, unfortunately leading the actors and production staff members to sometimes hit their heads on the ceiling. During production of Star Trek: Enterprise's first season, chief lighting technician Bill Peets observed, "Because the set is so low, we have a running joke: Who hit their head today? Some people actually wear hard hats now because so many people have cold-cocked themselves and gotten a lump on their noggins, including the actors. When you get to this set you've got to be careful." (Star Trek: Communicator issue 138, p. 51) Some of the furnishings in the set for Archer's ready room came from a French designer. (citation needed • edit)
All the prints in the series of Enterprise illustrations were made by John Eaves, who, due to his own oversight, had only 24 hours to produce the drawings. A fifth, that of the World War Two carrier USS Enterprise (CV-6) was additionally slated to be part of the series, but had to be left out due to space restrictions on the wall.  Set decorator James Mees recalled of the ready room, "We were trying to show that [Archer] was someone who had a past, a good past, and who remembered that past; that's what the show is so much about." (Star Trek: The Magazine Volume 3, Issue 3, p. 85)
On a Galaxy-class starship, the captain's ready room was located port of the main bridge, beside the forward-port turbolift.
The alcove where the replicator was located was supposed to open into a side corridor, leading to a bathroom. However, it was never shown on camera and a set was never constructed. The corridor, however, was briefly seen in TNG: "The Neutral Zone", showing Picard walking out of the corridor, back into the ready room proper. Also, the couch in Picard's ready room was actually constructed to slide out from the wall for use as a bed; though this function was never seen in use, it could occasionally be seen with the bed part either pushed too far into the wall or sticking out farther than intended.
An exterior shot looking into Picard's ready room, from TNG: "The Best of Both Worlds, Part II", "Darmok" and "Conundrum", showed the outside bulkhead of the ready room as squarish in shape. This did not match the configuration seen on the exterior model of the Enterprise-D. Also incorrect was the reflection in the window, proving a perspective that made it appear as though the ready room window actually faced forward.
In the film Star Trek Generations, the fish tank was seen blackened and apparently drained following the crash of the Enterprise. When asked what exactly had happened to Picard's fish, the producers admitted that it most likely perished in the crash.
Many of the scenes involving conversations in Picard's TNG ready room were filmed independently from scenes on the bridge, meaning that the latter wasn't always fully dressed, when seen from inside Picard's ready room through the open door. Oftentimes this resulted in the bridge set outside the door not being fully "ready" as a real bridge would be; many times, particularly during the last two seasons, the emergency turbolift alcove directly across from the ready room alcove was not lit and, in many cases, the two forward consoles were not staffed. Also, there were many instances when an actor would come to speak with Picard actor Patrick Stewart and then leave the ready room set, with the camera (and, therefore, the audience) remaining in the ready room with Picard; through the open doorway, the departing actor could clearly be seen walking towards the viewscreen. Within the Star Trek universe, those actors would have been stepping into a solid wall where the viewscreen was; as it was, the nine-foot-tall cavity where the viewscreen supposedly stood was actually the means by which actors entered and left the set, as it opened directly onto the soundstage. Only in scenes specifically requiring the viewscreen to be seen was the bottom of the screen frame – discernible by two vertical separation lines near the corners where that part could be removed – attached, and either a bluescreen matte or a starfield drape placed outside, to give the illusion of an image.
On an Intrepid-class starship, the captain's ready room was located starboard of the main bridge, beside the tactical station.
The desk, which featured a work area and access console, was the focal point of the room, located in front of the main entrance door. A raised level in the front section of the room featured a small table, a curved couch, and a food replicator.
The bulkhead behind the couch featured three windows facing the bow of the ship. A port-facing door beside the main entrance provided secondary access to the room from a deck 1 corridor. (VOY: "Shattered")
A shelf beside the main work desk allowed the commanding officer to display personal belongings. Captain Kathryn Janeway, of the Intrepid-class USS Voyager, used this shelf to display various historical and archaeological items.
The windows aboard the USS Voyager were a reuse of the windows seen in Ten Forward aboard the USS Enterprise-D, simply flipped upside down. The same was true of Voyager's briefing room.
For the production of Star Trek: Insurrection, Captain Janeway's ready room was redressed for use as CounselorTroi's office (somewhat appropriately, since Janeway's couch was first seen on TNG in Troi's Enterprise-D office). The set was also modified for the Voyager episode "Author, Author", lit with darker tones and decorated not with historical and archaeological items, but with weapons of various designs.
Aboard Sovereign-class vessels, the ready room was located to the forward starboard side of the main bridge. It featured a small window looking out into space and a private entrance located off the bridge.
Captain Picard's ready room aboard the USS Enterprise-E featured a desk and small couch. It was decorated with items from the previous Enterprise, including the Mintakan tapestry. (TNG: "Who Watches The Watchers") It also contained a large, gold model of the Enterprise-E herself, along with the Enterprise-D, C, B, A and original Enterprise.
While none of the TNG films ever really featured a clear shot of Captain Picard's ready room, publicity stills from Star Trek: First Contact did show evidence of the existence of a cylindrical-shaped fish tank that apparently did not make it into the final cut of that movie, nor any of the others.
The room was mostly unchanged in Star Trek: Insurrection. However, director Stuart Baird requested that it be redecorated for its appearance in Star Trek Nemesis, thus, the Mintakan tapestry was removed. Also, the small corridor leading to the bridge was slightly lengthened and the model of the Enterprise was added.
A section of the script for DS9: "Paradise Lost" takes place inside the ready room of the Excelsior-classUSS Lakota, but the same scene in the final version of the episode seems to take place on the ship's bridge. The Okinawa's ready room was mentioned in that episode but never appeared.
Worf and Martok are the only characters who were seen using both the ready rooms aboard the Rotarran and the Ch'Tang.
The concept of a ready room was first conceived by Robert Justman. He later recalled, "I suggested to Gene [Roddenberry] that we should have a captain's ready room, for what we both considered as a dramatic necessity. In a show like Star Trek, you need to have a place where the star, or the captain, can go to have a privileged conversation with someone else, without the possibility of being overheard. To me, the ready room was the perfect place to have that." (Star Trek: Communicator issue 115, p. 74) Justman took the idea from Navy experience he himself had had. 
James Mees was of the opinion that the identity of a ready room's occupant should inform how the room itself looks. "My question is this: Does a ready room always have to have a desk, a chair, and a place for someone else to sit, or does the form and function of the room vary between races?" Mees asked. "To me, it seems clear that different people need different spaces. For instance, Degra's Ready Room is more a working laboratory than an office, because that's what he wants and needs." (Star Trek: Communicator issue 152, p. 36)