[size=4]Which seats do you use for short, medium and long range and in which aircraft model? How I can know if I [color=#000000]chose right kind of seats?[/color][/size]
First you have to look if there is a lot of competition in your airport. If you are the only airline in your country for domestic (short-haul) flights you can use standard seats for economy and business class because people will want to fly.and there will be no one who offers better services so you will get all passengers with minimum expenses.
For medium and long you should look at how many others fly to that destination?
What is there rating in ORS? (if it is high you will have to put better seats to get PAX
Are all flights full in ORS? If all flights are full you can use bad seats and still get PAX as there is too much demand and supply is low.
There is no best strategy for everyone. You should choose that you think is best and with time you will be able to choose the best seating configuration.