Accommodation
Where
Do you want to visit the city and monuments? Then search the place where to stay just in the center. You can move easily by bus or just walking avoiding renting a car.
If you rent a car then better avoiding just the center due to some traffic limitations and then search just close to it.
To get an idea of the center of the city then have a look at this map.
Instead if you are going to Palermo to get a wonderful sun&beach holiday a perfect spot for an accomodation is Mondello, a seaside borough of Palermo characterized by a white sand beach.