a snake inside your tent is RARE in Australia - but wise to check before entering
the venomous Australian snakes are generally not active at night unless it is a very warm night (ie. they are diurnal) - they are NOT likely to crawl into your sleeping bag with you - I have never heard this happening in Australia, but eastern brown snakes in Queensland have been known to get into beds in a house
non-venomous pythons (these are the most common snake as a pet) live in trees and are active at night but are rare in southern parts of Victoria being mainly found north of Wangaratta and along the Murray River system and latitudes north of this - a third of houses on the Gold Coast in Qld have a python living in the roof!
snakes are generally well-natured and they will avoid humans whenever possible, although may remain still if they sense nearby danger
whilst they are common they are usually only a danger if one does not see them whilst walking and steps on or near them, or is stupid enough to try to catch them without training
they are not going to chase you but may come towards you if you are between them and their preferred safety destination - just move sideways out of their way or stay completely still - biting you is usually their last defensive resort
they avoid exposed open areas and prefer longer grassed areas, vegetation, or fallen trees (however, in the morning they will often bask on paths to get direct sunlight)
snakes are more common near waterways where they have a better food source in frogs, lizards and rodents and generally more vegetation for shelter
snakes are far less active in the colder winter months in southern parts of Australia
on warmer days they occasionally will seek shelter under or inside a tent, or under a vehicle (especially on a warm day where there is little other shade they can access safely)
reduce snake issues in or near your tent by:
pitch tent in an open area with low grass or no grass and away from bushes, fallen trees and branches
if you are leaving your tent up during the day:
zip it up and seal any holes - assuming it has a floor
if it does not have a floor or you have a large tent, consider having a sealed 2P tent inside in which you can store your sleeping gear and sleep in
keep the floor of your tent tidy so it is more easy to spot a snake when you enter
do not have open food in your tent, this attracts mice and birds which attracts snakes (snakes themselves are not attracted to human foods though)
on returning to your tent:
check the outside for snake tracks or a snake tail sticking out from under it (if possible lift the tent up to check under it)
check the inside before entering
if your sleeping bag is not in a sealed tent, take it outside and carefully shake it upside down away from you - better still use a quilt or leave the sleeping bag fully open
if you are paranoid, consider white vinegar around your tent as this is said to reduce snakes as they don't like slithering over it - not sure if there is good evidence for this though!