In "Emissary," the station DS9 is moved from orbit around Bajor to the entrance of the wormhole- but without any stellar body there for it to orbit, what's keeping the station from drifting away?
Both the wormhole and Deep Space Nine are in orbit of Bajor-B'Hava'el, the central star in the Bajoran Star System. The station has thrusters that allow it to make small corrections and remain in constant proximity to the wormhole itself.
Map Courtesy of the Star Trek: Deep Space Nine Technical Manual
The original script for DS9: Emissary indicates that the station has been moved about 160 million kilometres from its original position (which, for reference is about 80% of the mean distance between Earth and Mars). Its new location is still well within the same star system.
O'BRIEN: This isn't a starship, Major. We've got six working thrusters to power us and that's it. A hundred-sixty million kilometer trip would take two months.
KIRA: It's got to be there tomorrow.