Keep left

Coming to Australia from Greece I had the problem to adjust to left side driving. Today about 66.1% of the world's people live in right-hand traffic countries and 33.9% in left-hand traffic countries. About72% of the world's total road distance carries traffic on the right, and 28% onthe left.

source

It took me about a month to get comfortable on driving to the other side that I used to drive for 20 years. 

Australia drives on the left. The decision to drive on the left side of the road was made in the early 19th century in the early period of the British colony of New South Wales.

Keep left sign on the Great Ocean Road, Victoria

Thankfully roads in Australia are well signed, equipped also with pavement markings and lines making it real easy for the foreign driver to drive here. The most helpful sign is without doubt the KEEP LEFT sign.  

The sign is used near the start of a central island, median or similar device where traffic can physically pass on either side but it is necessary for all traffic on the particular approach to pass it on one side only.

The sign and the left arrow is also used in other occasions. It seems that the last days everywhere I go I find one of this in front of me.

Bermuda Road, Gold Coast

Q1 Gold Coast

Australia Fair Parking, Gold Coast

Gold Coast Highway

Gold Coast Highway

Victoria Bridge, Brisbane