When do pilots deploy landing gear?
As late as possible to still meet your company's specific stabilized approach guidelines (mine were 500 ft VMC, 1000 ft IMC).  If you need the drag, then use them earlier.  

In the EMB-145 in still wind or a headwind you could cross the FAF at 250 kts and clean and be on speed and configured by 1000' if you dropped the gear at the FAF (and opened the speed brakes and the first notch of flaps all at once).  Normally though, I'd drop the gear around 1000'.

Acronyms:


VMC = visual meteorological conditions
IMC = instrument meteorological conditions
FAF = final approach fix
EMB-145 is the type designator for the Embraer 145 regional jet