Don't think that your religion is purely a matter of choice. Deep things go on inside people that lead them to certain beliefs or ways of living. The important thing is to be true to yourself and not to be afraid of the truth.
Seek more reality, more consciousness.
That aside, there are lots of different religions to choose from. The main ones in Australia are Sport, Family, Your Country, Money, Your Job, Improving Yourself, Christianity, Aboriginal Spirituality, Judaism, Islam, Buddhism, Hinduism, New Age, Seventh Day Adventism, Mormonism. There are heaps more...
Your religion is what is most important to you in your life.
Many people say they believe in God but then act as though God is not as important as themselves. If you can find someone who does believe in God and does put God first then talk with that person about your options. She or he will be able to tell you what it's like to have a faith that is real.
Apart from that you can ask God yourself.
Even if it feels a bit silly or weird, try it. You probably won't get an answer straight away...a big voice won't boom in your head. But if you practise trusting God, even if you don't believe in her (or he or it) then you will eventually get in touch with the deep wisdom within us all that helps us know how best to live.