Andromedan was a demonym which meant "someone from the constellation of Andromeda". Since it included beings from different planets, such as Salostopus, it did not actually suggest a single species or culture. (TV: The Trial of a Time Lord, PROSE: The Ultimate Foe)
The Second Doctor recalled an old friend of his that, last he heard, was selling illegal fake TARDISes to the Andromedans. (PROSE: Invasion of the Cat-People)
Some Andromedans were known to have lived on Earth for a while, and later ransacked the Matrix on Gallifrey. This act was one of the proximate causes for the Sixth Doctor being put on trial. (TV: The Ultimate Foe) The criminals Sabalom Glitz and Dibber were also Andromedans. (TV: The Mysterious Planet)
Andromedans were used to travelling long distances in suspended animation. Such Andromedans were called "sleepers". (TV: The Ultimate Foe)
The Ninth Doctor claimed to have watched the Andromedans invade the Hagon Cluster, and sent them scurrying back. (PROSE: The Red Bicycle)