Please submit your application to the Schengen country that is your main travel destination. If you are visiting only one Schengen country, you should apply for the visa at the Embassy or Consulate of that country.
If you are travelling for business or official purposes and plan to spend some time as tourist as well, you should apply to the country where your business or official purpose takes place. E.g. you have a business trip of four days in Norway, and then wish to visit France and Spain for tourism for five days in each country, you should apply for a visa to Norway, as this is the main purpose of the trip.
If your itinerary contains several Schengen countries, please apply for your visa at the Embassy or Consulate of the country of your main destination, i.e. where you intend to spend the most days. E.g. if you are staying for ten days in Norway, then travelling on to Germany for five days, and another five days in France, you should apply your Schengen visa from Norway as you will spend most of your stay in Norway.
If you intend to visit several Schengen countries, but do not have a main destination (i.e. you intend to spend an equal amount of days in each country), you should apply at the Embassy or Consulate of the Schengen country which is your first port of entry. So if you are first travelling to Germany for five days, then France for five days and finally Norway for five days, you should submit your application to the German embassy.