Buying a bike is a bit like buying a surfboard or computer - just because it looks good, doesn't mean it's the best choice for your needs and your level of experience. So try out a few different bikes. Get some advice from more experienced riders. And remember a few basic rules:

Standard/naked/street bikes have an upright riding position and are mainly used for commuting.
Cruisers have a relaxed upright seating position and plenty of chrome! Riding position is feet placed forward.
Tourers or touring bikes are designed for making long distance rides more comfortable and practical, with capacity for luggage, bigger fairing or a windscreen for wind protection.
Electric motorcycles are environmentally-friendly and quiet, but are sometimes limited in speed by battery capability.
Mopeds have up to 50 mL engine power and a top-rated speed of not more than 50 km/h.
Scooters generally have a step-through frame, automatic transmissions and smaller wheels than most other motorcycles. Engine size can range between 50 mL and 600 mL.
Off-road motorbikes are generally lighter with higher ground clearance and better suspension.
Dirt or adventure bikes, including trail and enduro bikes, are usually used in long distance competitions or obstacle competitions (Motocross).
Supermotos have street wheels and tyres, and some of these can be registered for riding on roads.
Racing bikes are fast, light motorcycles with a rider's tipped forward position, designed for circuit or road racing. They can also be highly customised.

The Glovebox Guide has lots of good information about buying a new or used motorcycle. It's available from the Office of Fair Trading.
You can also access Queensland Transport services which check the history of your motorcycle to protect you from potential buyer risks such as if it has been lost, stolen or there has been water damage or if money is still owing on it.
If you're thinking about buying a second-hand motorcycle, it's a good idea to consider purchasing a Vcheck before you buy. It's a quick and easy way to find out important information like:
If you have a Queensland drivers licence or Queensland Transport customer reference number, you can purchase a Vcheck online through Queensland Transport.