[arunix]

TNG introduced various civilisations that drive much of the plot in DS9.

Season 1: Ferengi

Season 4: Trill, Cardassians

Season 5: Bajorans

Also, Chief O'Brien and his wife Keiko who were recurring minor characters in TNG have more important roles in DS9.

[Izkata]

Don't forget Worf also moved over when TNG ended.