Fulfil the required task to unlock the corresponding achievement, there are nineteen in total.

Achievement	How to unlock
300	Play 300 games
Bakers Dozen	Play on 13 Consecutive Days
Black Jack	Play on 21 Consecutive Days
Boiling Point	Play 100 Live games
Buddy Buddy	Play 10, two player games
Century	Play 100 games
Contender	Completed 10 tracks the whole way through
Hat-Trick	Play on 3 Consecutive Days
High Five	Completed 5 tracks the whole way through
Hundred K	Scored over 100,000 points
Lucky Number	Play on 7 Consecutive Days
Millenium	Play 1000, two player games
Most Wanted	Play 10 Live games
Playing with Fire	Play 1000 games
Polaroid	Played 25 songs with Shakes on
Still Tappin'	Played 25 songs with Shakes off
The Regular	Play 1000 Live games
The Rookie	Completed a track the whole way through
You Have Friends	Play 100, two player games