In some countries I've had difficulty finding a place to stay for the night. The fault has been mine. I've been too casual, expecting to turn up at a new location and find a motel or campsite without difficulty.
In Australia you can often do that. In many places there's a lot to choose from and you can shop around for the best deals. There are, of course, exceptions to this general rule.
Hotels and motels: Except in major cities, the term hotel usually refers to a pub. Historically, hotels were obliged to provide accommodation. Outside major centres, few do today. In country areas, look for motels. Your will find them on the main roads leading into towns and scattered along highways. Many motels are attached to old hotels. Go to the tourism web sites to get an idea of what is available.
Camping resorts are plentiful and standards are high compared with many countries. Individual caravan sites usually have power outlets and some have their own shower/toilet annexes. Many resorts have cabins for rent on an overnight basis. Camp kitchens (pictured above) and barbecues are generally provided. Laundry, shower and toilet facilities are required by law. Many resorts belong to organisations. Their web pages are easily found. Some are geared towards families, some to older people and others to young adults. As a general rule, avoid campsites that are primarily residential. You could hit unlucky and find yourself entangled with the neighbourhood's social problems.
Serviced apartments have a day room, bedroom(s) en-suite and kitchen. The larger accommodate six of more people. The cost per person can be less than dormitory accommodation in a backpacker hostel and you can save money by doing your own cooking. When my wife and I visit a major city, we prefer to stay in a serviced apartment rather than a hotel. Advance booking is recommended but not always essential.
Cottages are available in many rural areas that have experienced a decline in population. They are usually rented for a number of days (rather than overnight) and are one of my wife's favourites. Advance booking is recommended.
Outside school holidays you can generally find overnight accommodation in the larger centres without forward booking. This means you can turn up and look for a good deal but don't leave it too late (after 4pm, say). If you are travelling in a busy period or visiting a remote location, secure accommodation at least a day in advance.