Art diler mozer byt 'vladel'tsem galerei.
A esli i net, to upotrebliaet te ze samye metody: invests in advertising, catalogs, magazines, albums, organizing exhibitions, etc. Gallery of the public, it's interviews, press conferences, media coverage.

Added after 45 seconds
Esli hochet uspeshno rabotat '.

AlexanderG, Vivian, agree, sometimes this way and that ...
I rely on their own experience and traditions of the art market.

That's right. It happens to everyone. The question was specifically about the differences between the gallery of art dealer. Art dealer may not have gallery (room).
A gallery without art dealer in the face of the owner or director can not exist.

We are a little deviated from the main theme of the post :)