It all starts with basic identifying information, such as your name and your address. You may be asked to provide a piece of mail with your address on it - such as a bill - to show that you really do live there. If you live in Australia, you need to tell the company which province you live in as well, though overseas traders may not be asked for the same details if their countries are not divided with a similar system. This address will be used to give you your tax information at the end of the year.
Next, you need to give out contact information. The most useful bit will be your email address. This will be a quick way for you and the broker to communicate about anything at all, from buying new stocks to cashing out your account if you have done well. You may also be sent confirmation emails whenever you place a trade so that you can keep records of what you have done with your money. On top of that, you will probably use your email address whenever you decide to log into your account, along with a password that you have created.
Finally, you need to provide financial information. How do you want to transfer funds into your new account? Do you want to use a debit card or route the money straight from your bank account? Do you want to use your credit card? When you get the money, how do you want it to be sent to you? These are all good questions to ask yourself when deciding what financial information to provide. Once this is done, you can move money to and from your account, and you can start using that money to place your trades.