Benjamin Sisko is the Captain of the Defiant, Commander of DS9, and the Emissary(spiritual leader, chosen by the Prophets and called "The Sisko") of the Bajoran people. He is a good, strong leader of both his peoples. He has a son named Jake on the station and a father back on Earth. He was very close to Dax because he knew her in her last life as Curzon Dax, thus he affectionately called her "Old Man". Benjamin loves cooking & baseball.
Colonel Kira Nerys is a loyal Bajoran. During the Occupation, she played an active role in the Resistance, engaging in many terrorist activities against the Cardassians. She is the Bajoran in charge of DS9, sharing the responsibilites of running the station with Sisko. She is known for her many lovers, but is currently involved with Odo. Nerys is an excellent fighter, and deeply devoted to the Prophets.
Lt. Cmmdr. Worf previously served as Head of Security aboard Picard's Enterprise and now does the same thing on the station. He married Jadzia Dax, who was the Trill Ambassador to the Klingon homeworlds in her last life. Worf is a typical Klingon--war-like & loyal with a deep sense of honor. He was "adopted" into General Martok's House, as was Jadzia at their wedding. He has trouble dealing with Ezri because she has all of Jadzia's memories.
Odo is Security Chief on DS9. He is a changeling, as are the Founders of the Dominion, and was torn between his love for a solid (Nerys, who he is currently involved with) and his need to be with his own kind (the Founder) during the Dominion & Cardassian Occupation of DS9. Odo is the extremely responsible type, with a dry sense of humor and sharp wit. Odo's personally assigned duty is seeing that Quark stays out of trouble. When those two are together, there is a mutual respect and animosity.
Dr. Julien Bashir is the perfect man. He was genetically altered as a child, and is now a genius. He is witty, charming, generous, loyal to his friends, devoted to medicine & good-looking to boot! He was once in love with Dax, but got over it sometime before she married Worf. He has recently fallen in love with another genetically enhanced individual, Serina.
Miles O'Brien is just a great man. He is Chief Operations Officer on DS9 and knows the station inside-out (like no one else.) He and Julien are best buds and spend their free time together in the holo-suites or playing darts at Quarks. Miles is a wonderful husband, caring father & good friend (not to mention one heck of an engineer.)
Lt. Ezri Dax made her DS9 debut in the 7th season's premiere episode, Image in the Sand (which was continued in Shadows and Symbols). She is a Starfleet officer and a counselor. So far she has befriended Sisko, helped Garak with his guilt-caused claustrophobia and is currently the romantic interest of Quark.
Nog was the first Ferengi in Starfleet. He is the son of Rom and the nephew of Quark. His dream came true when he got to be a member of Red Squad (top Starfleet Academy cadets) on active duty in Dominion space. His buddy, Jake, was with him at the time and was less than joyous at their predicament. Nog lost a leg in the war against the Dominion, but is expected to recover. He is as un-Ferengi as his father.
Quark is the proprieter of Quark's (a bar) on DS9. He is a Ferengi who is totally devoted to his Rules of Acquisition. However, Quark has a highly developed sense of honor, although it is usually hidden by his typical Ferengi greed, and is a loyal and courageous friend. He was in love with Dax, although he wouldn't admit it (either due to the fact that love can be dangerous to one's profits, or that Dax was married to a very strong and hot-tempered Klingon warrior!) Quark has an engineer brother and a Starfleet Ensign nephew (highly irregular for Ferengis) on the station, so he feels that he must be extra Ferengi-like to compensate!
Keiko O'Brien is a botanist who is married to Miles. Together they have two children, Molly (the oldest), and Yoshi (their little boy). Although Keiko is not a major character, I have gathered that she is a gentle, warm and loving individual, perfectly suited to that equally gentle, warm and loving husband of hers.
Jake Sisko is a journalist and the son of the Captain. During the time that Cardassia and the Dominion held DS9, he stayed on the station and reported the events that took place. His best friend is Nog.
Garak is a Cardassian tailor aboard DS9. He was once a highly placed official in the Obsidian Order, but he crossed the wrong people and was banished from Cardassia. However, he still has some connections, and knows how to use them. He was in love with Dukat's daughter, Ziyal, and she loved him even more, therefore he was very hurt when she died. He is wily, witty and refined (for a Cardassian).
Rom is a Ferengi engineer. He used to work for his brother at Quark's, but was hired by Miles for his amazing knowledge of engineering. He recently married a Bajoran named Leeta, who works for Quark.
Leeta works for Quark in his bar. She was in love with Rom, but didn't know whether he felt the same. She tried to get him to say something, but when he didn't she decided to leave the station with Dr. Zimmerman. Rom stopped her in time and they are now happily married.
General Martok, a battle-hardened warrior is a great friend and adopted father to Worf. The two fought against the Dominion together aboard Martok's Bird of Prey.
Gul Dukat is the one person the Kira hates more than anyone else in the quadrant. He was an official during the Cardassian Occupation of Bajor. He is a quite likable guy, if one can overlook the fact that he is insane. When his daughter, Ziyal, (who I want to believe was Nerys' half-sister) was killed during the most recent Cardassian occupation of DS9, he lost what was left of his marbles! Anyway, Dukat managed to evade Starfleet and blames all of his misfortunes on Captain Sisko. He is also the reason that Jadzia is dead.
Jadzia Dax was the Science Officer on DS9. During the rough part of the war, she was given command of the Defiant, while her then fiancee, was serving aboard General Martok's ship. Jadzia was a Trill and host to a sembient called Dax. The sembient retains the memories of each of its hosts and therefore the host remembers. Dax has been a parent 9 times over, 4 as a father and 5 as a mother. She was killed in last season's finale, Tears of the Prophets, by Dukat (who also managed to "kill" the Prophets.)
Ziyal was the daughter of Dukat. She was in love with Garak and sided with the Federation when the Cardassians retook DS9. She was killed by her father's second-in-command, Damar.
Vic Fontaine is a holoprogram. He sings in a snazzy little club and always knows what to say to help a person out. He is unique in that he is aware that he is a holoprogram and does have some control over his own program.
Weyoun is a Vorta from the Gamma Quadrant. He is actually a clone and is obsessively devoted to the Founders. He especially reveres Odo, causing the changeling no end of trouble.
Kasidy Yates is a freighter captain. She visits the station frequently and is Captain Sisko's significant other.
Damar was Dukat's second-in-command. He killed his superior's daughter for being a traitor, and subsequently took over control of the Cardissian end of the war.
Nagus Zek is the eccentric financial leader of the Ferengi.
He is also the significant other of Quark and Rom's mother.