During our time in Sighisoara we used a free map from the Tourist Information Centre. I actually had taken this map on a previous trip from the tourist information office in Brasov.
However, I noticed that also the Touist Information Office in Sighisoara's citadel had the same map available.
In Sighisoara we found a small tourist information office at the northern side of the Museum Square (Piata Muzeului). It provided several free maps, brochures and magazines, not only about Sighisoara, but also about other destinations in Romania.
Like many other countries in Eastern Europe, Romania is a rapidly developing country. Unfortunately, it is often difficult to find a Tourist Information Office or just a free map, therefore an up to date guide book is highly recommended, especially for independent travellers.
On all our trips to Romania we used the German travel guide Reise Know-How - Rumänien und Republik Moldau which was very helpful. Unfortunately it is not available in English.
Another very useful travel guide is Trescher Verlag - Rumänien entdecken . Also this book is, to my knowledge, only available in German, but regarding descriptions of the sights it is the most comprehensive.
Reise Know How: http://www.reise-know-how.de/
Trescher Verlag: http://www.trescher-verlag.de/