1. From Australia to PNG and return,
Book online with Airlines PNG. http://www.apng.com
2. From Asia to PNG and return,
Book with Air Niugini. http://www.airniugini.com.pg
3. For Domestic Air Travels,
Not Cheap. You need to plan that well in advance. Air Niugini and Airlines PNG just service the major ports and towns.
4. Travel Precautionary Measures.
So long as you are in the company of trusted hands, you will enjoy PNG. In PNG, particularly the rural areas, though life seems difficult, generally our people are caring. Do not waste your time in Port Moresby, Lae, Rabaul and Mt Hagen. Visit other areas and you will truly feel and see PNG. It just depends on the local calendar.
My definition of trusted hands, give yourself plenty of time and allow your intuition to check out those so called trusted hands before you commit yourself.