Alston grew up in Jamaica, Queens, New York and was a standout streetball basketball player, known for his nontraditional moves which made him particularly adept at getting past defenders while dribbling the ball. He was the inspiration in many ways for the AND1 Mixtape Tour—a low-quality, jerky 1999 videotape of Alston's extreme playground moves, featuring helter-skelter crossover and other fast dribble moves faking out defenders, attracted a great deal of attention among players and basketball fans. These unique moves became Alston's signature, and in fact, his nickname "Skip 2 My Lou" comes from one of the moves. As the video began to circulate (some can be seen on AND1 Mixtape Volume 1), other non-NBA players began to contribute their own moves and highlights, and eventually the AND1 Live Tour (originally the AND1 Mixtape Tour) developed from that beginning.
Alston played basketball under coach Gregory Adams at St. Jerome School in Bronx, New York. He also played under famous high school coach Ron Naclerio at Benjamin Cardozo High School in Queens, New York. Naclerio is credited with circulating the Alston tape and getting it in the hands of AND1 staff.
Alston played college basketball for three seasons: one each at Ventura College (1994–95), Fresno City College (1996–97), and Fresno State (1997–98). Alston was red-shirted at Fresno City College for the 1995-96 season.
Alston struggled early in his NBA career, but successfully transitioned from streetball to the professional game. After playing off the bench for most of the time he was with the Milwaukee Bucks, he was traded to the Toronto Raptors. Following his tenure with the Raptors, he emerged as a starter for the Miami Heat in 2004. He did not disappoint, averaging 12 points and 4 assists on a young Miami team, led by rookie guard Dwyane Wade, that made it to the Eastern Conference Semi-Finals of the NBA Playoffs. During that season, in a March 26 game against the Dallas Mavericks, he hit a game-winning shot in overtime with 0.5 seconds left over the outstretched arms of Shawn Bradley to catapult Miami to a 119-118 victory. Alston would sign a multi-year deal with the Toronto Raptors in the summer of 2004. For Alston this was his first step in the new phase of a secure NBA career which had eluded him until that point.
Alston was traded to the Houston Rockets for guard Mike James on October 4, 2005. Although Alston frequently was criticized for his attitude while in Toronto, it is believed that Rockets coach Jeff Van Gundy conferred with his brother, Miami Heat coach Stan Van Gundy, who coached Alston during the 2003–04 NBA season, about Alston's work ethic and attitude. Jeff Van Gundy's reputation for toughness and his ability to get the most out of players previously considered "trouble-makers" or "temperamental" (e.g., Latrell Sprewell) led to optimism on the part of the Rockets' staff. In the 2006–07 season, as the Rockets starting point guard, Alston averaged 13.3 points, 3.4 rebounds, 5.4 assists and 1.6 steals per game. He finished the season ninth in steals among all NBA players, fourth in three pointers made, and 23rd in assists. On November 12, 2008, Alston was suspended for two games without pay for his role in a fight after a non-call foul with Matt Barnes and Steve Nash.
Alston was traded to the Orlando Magic in a three-way deal on February 19, 2009, and replaced the injured Jameer Nelson in the team's starting lineup. On April 30, 2009, Alston helped the Orlando Magic defeat the Philadelphia 76ers 4-2 in the first round of the NBA Playoffs. Orlando then defeated the Boston Celtics and Cleveland Cavaliers to advance to the NBA Finals, where they lost to the Los Angeles Lakers in five games. Alston averaged 10.6 points, 3.0 assists, and 2.2 rebounds in the Finals.
On June 25, 2009, he was traded to the New Jersey Nets along with Tony Battie and Courtney Lee in exchange for Vince Carter and Ryan Anderson. He had his first triple double as a member of the New Jersey Nets in 2009-2010. On January 5, 2010 he was released by the Nets in hopes of letting him play for a contender.
On January 7, 2010, he cleared waivers and signed with the Miami Heat for the second time. After starting 25 games for Heat, he was immediately suspended on March 6, 2010, for missing practice and a game. On March 13, 2010, Miami upgraded his suspension for the remainder of the season.
On January 26, 2011, Alston signed with the Zhejiang Guangsha in the CBA for the remainder of the season. In late February, it was reported that he had left the team to attend a friend's funeral, and the team, believing he was unlikely to return because he had been injured and refused to see a doctor, told him to not return. Alston never appeared in a game for Guangsha.
In 2012, Alston signed with the Los Angeles D-Fenders of the NBA D-League. This would be his last run as a professional basketball player.
On Sunday morning, August 5, 2007, Alston was arrested in downtown Houston on misdemeanor charges of assault and public intoxication. He was arrested again early Tuesday morning, August 28 in New York for allegedly slashing a man on the neck during a nightclub altercation. Neither the club owner, police, nor security tapes have provided any evidence of the incident occurring. The charges brought against Alston for the incident that took place on August 5, 2007 were dropped on February 29, 2008.
"We went into court, and the DA office indicated that all charges be dismissed based on their investigation," Al Ebanks (Alston's Lawyer) said. "They did not feel this is a case that should go forward. We're obviously pleased with the outcome, as pleased as can be when the case had no merit and understand should never have been charged in the first place."
"Al and a lot of my family members were worried if I could go on with the season, would it be on my mind," Alston said. "When you know you didn't do anything, I just waited for it to be over and came in and focused on basketball."
"You can deal with things when you know you didn't do it. Now the whole case is over with, and they want to keep it silent. I was on the front page when it happened."
"Now when it's dropped they want to keep it silent. That's OK. I can deal with that. That's not who I am."
He was arrested again on August 7, 2008, and charged with DWI.