Australia

Visa: The most common visa among travelers (who aren't Europeans) is a six months visa, which can be renewed four times by leaving the country and then returning. In case you applied for that kind of visa, you should be very aware of its validity dates and plan your time accordingly.

Plan your trip according to the climate in the various parts of the continent. For example: if you are planning to travel along one of the coasts it's better to travel from north to south at the end of the winter or the spring so you'll get to the southern parts of the country when the weather is warmer.

Driving in Australia is on the left hand side of the road. Travelers often underestimate the distances between towns and cities, and the amount of time it takes to travel by road around Australia. If you intend to drive by yourself through more than one state, do so only if you are a competent and experienced driver. Before every long drive, check your car and make sure to have a first aid kit and a spare jerry can of fuel and water.

Flights within Australia: if you intend to fly within the continent it is recommended to use one of the following companies:
Tiger Airways: http://www.tigerairways.com
Jet Star:           http://www.jetstar.com/  
Virgin Blue:      http://www.virginblue.com.au/
Be aware that the prices differ according to the season and to the time of booking.