Nizamabad is well connected to Hyderabad by both rail and road. Nizamabad Junction railway station has regular trains to Hyderabad (roughly 3 to 4 hours on most services), and the route is served frequently enough that you can travel without booking far in advance.
By road, the distance from Hyderabad is about 150 km via NH 44 (the old NH 7). The drive takes 2.5 to 3 hours depending on traffic leaving Hyderabad. Buses run frequently from Hyderabad's Mahatma Gandhi Bus Station (Imlibun) to Nizamabad Bus Station in the city centre.
There is no airport at Nizamabad. The nearest major airport is Rajiv Gandhi International Airport in Hyderabad.