It's at best a fairly uncommon sight in the lower 48. If you get up further north it becomes far more likely that you'll see them. Fairbanks, AK or Whitehorse, YT are good destinations for catching them (during the winter, not so much during the summer due to the lack of night).
Auroral activity tends to be greatest around the equinoxes, but other factors are at least as important. You need a clear, cloudless night. Winter months are better than summer months because of the length of the nights vs. days. The level of recent solar storm activity and related solar phenomena greatly affects the aurora, of course, but is hard or impossible to predict beyond the overall 11 year solar cycles.