Currently, I'm doing the Thieves' Guild's radiant quests, working to unlock the next set of quests.
The quests that Delvin give you to "retake" some cities, adding merchants to the Ragged Flagon. These are the prerequisites for becoming the official Guild Master.
So far, I've managed to unlock (and complete) 3 out of 4:
I've done the quests for Whiterun, Windhelm, and Solitude. Only Markarth is missing now.
However, I can't seem to get the last few radiant quests in that area, which I need to unlock the final assignment. I've accepted and cancelled dozens of jobs with both Delvin and Vex (Around 30 - 40 each), but the one city I still need to advance simply never shows up.
Is my luck just that bad, or is there something else preventing me from getting any jobs in that area?