Basics for optimization:
– clean frequency planning (no interference)
– all neighbours are correclty defined
– avoid same bcch/bsic among cells of the same LAC (or at least the same geographical area)
– check orientation and tilt of antennas, so that coverage is good, but not too much overlap in cities.
Once you’ve done that, your netwtork is optimized at 95%
Final step : check all your radio parameters are set to their default values (cf your vendor documentation)