William Thomas Riker served as First Officer on the Enterprise-D. He made no secret of his ambition to be its captain in the future. He passed up more than one promotion to stay with the Enterprise crew, most notably to take command of the USS Melbourne. Eventually he did accept an offer to command the USS Titan.
Riker's first assignment was aboard the USS Pegasus under the command of Eric Pressman, during the illegal development of the phase cloaking device. At some point, crew of the Pegasus refused to continue their engagement in the violation of the Treaty of Algeron and mutinied. Riker defended Pressman and together with Pressman and a few other crew members, managed to leave the ship in an escape pod. They believed they witnessed the destruction of the ship. The incident was covered up until Starfleet learned that the Pegasus had not been destroyed, and Admiral Pressman took the Enterprise-D to recover the illegal device on board. Riker finally decided to reveal both the truth and the device to Captain Picard who revealed it to the Romulans. We do not know what happened in the aftermath of this revelation of a severe treaty violation.
The entity Q once became impressed with Riker. Making a bet with Picard, Q briefly gave Riker the same powers the Q possess. Through the rest of the crew rejecting the favors Riker performed for them with Q power, Riker himself rejected Q's offer.
Riker is considered an exceptional pilot, chiefly because he is one of the few people in Starfleet who can fly a shuttle manually. He was able to fly through a nebula and plant mines on several threatening Cardassian warships, Riker briefly commanded the Enterprise after Picard was captured and assimilated by the Borg. His combat tactics against the cube were less than spectacular, consisting of a slow turn. Those tactics didn't show much improvement when the Enterprise was attacked by an obsolete BOP, resulting in the destruction of the ship's stardrive section and the saucer crash landing.
Riker is the only human known to have served as a temporary host to a Trill symbiont.
Before his assignment to the Enterprise, Riker once had a romantic relationship with Deanna Troi. The former relationship seems a point of friction in the early days of TNG, but it never causes any serious problems, even when Riker is "the big lady's man on the ship" or when Worf and Troi begin their short-lived romance. Possibly inspired by the fountain of youth discovered around the Ba'ku planet, Riker and Troi renew their relationship and eventually marry
Riker has a strained relationship with his father, chiefly due to his mother dying at a young age. His hobbies include playing jazz trombone and poker. When playing cards with him, its a safe bet he's bluffing.
While leading a rescue mission, a duplicate of Riker was created by one of their many technobabble transporter accidents. The twin was stranded on the planet following an evacuation and rescued years later by the Enterprise. The twin differentiates himself by using the name Thomas, Riker's middle name.