Worf "Son of Mogh" was born on Qo'noS (pronounced Kronos) the Klingon home world in 2340. In 2346 when he was 6, Worfs family left Qo'noS and moved to the Khitomer outpost.
Worf's family have a high standing in Klingon society. Years earlier when Captain James Kirk and Dr Leonard McCoy are accused of assassinating the Klingon Chancellor, A member of Worfs family defends them at their trial.
Shortly after arriving at their new home, the Romulan Star Empire attacked Khitomer and 4,000 Klingons were massacred. Although his family perished Worf survived.
A Federation ship, the USS Intrepid responded to the outposts distress call. Arriving to late the Intrepid found chaos and devastation. Searching through the wreckage a Chief Petty Officer, Sergey Rozhenko rescued Worf. Assuming Worf's entire family had died Sergey and his wife Helena adopted the young Klingon boy.
They first lived on Gault a farming world. And later returned to Earth.
As the only Klingon child in his school (and perhaps even on Earth) Worf gained a reputation as a hell-raiser.
Despite his problems fitting Worf grew up and became the first Klingon to Enter Starfleet Academy.
Given that most people spend 4 years at the Academy, Worf must have signed up in 2357 as he graduated in 2361.
Worf's first major posting came when he was a Lt (Junior grade) and was assigned to the Federations new flagship The USS Enterprise NCC 1701-D in 2364.
His first position was as Conn officer (basically the pilot).
On the Enterprises first mission circumstances arise requiring the ship to separate. This involves the Saucer section of the ship parting with the Drive section.
Worf is put in command of the Saucer section of the ship. Giving him an early taste of Command.
After the tragic death of Tasha Yar, the ships Security Chief Worf is promoted to Full Lt and the ships new Security Chief.
Worf serves on the Enterprise NCC 1701-D for the ships entire existence. The Enterprise is destroyed in 2371. In his 7 year service he rises to the rank of Lt Commander.
After the Enterprises destruction Worf takes an extended leave of absence and travels to the Klingon monastery of Boreth.
In 2372 on DS9 a conflict with the Klingon Empire looks inevitable and Cpt Sisko (DS9's Commanding Officer) requests Worf be temporarily assigned to DS9. He assignment there is soon made permanent and a post is created for him.
He is the stations new "Strategic Operations Officer". He is also assigned as the Defiants Executive Officer. (The USS Defiant NX-74205 is the Starship assigned to protect DS9)
In 2374 after a long friendship Worf and Jadzia Dax marry in Quarks bar. At the close of the year Jadzia is murdered by Gul Dukat and Worf slips into a pit of depression. When the Federation / Dominion war ends Worf is made Federation Ambassador to Qo'noS.
He's saddened to leave DS9 after 4 years but relishes preserving the treaty between the Federation and the Klingons for many years to come!