When you register a trademark it is the first step in creating a new brand.
Only a registered trademark will give you an enforceable legal ownership of your brand.
Here's some trademark related resources to help you research a new trademark prior to registration and to help protect your brand post registration.
ATMOSS is the Australian Trademarks Online Search System.
This is where you search for pre- existing trademarks, pending trademarks, and expired trademarks. There are a range of specific searches you can do, including;
IPAustralia is the official Governmental body that administers, manintains and decides on disputes in the Australian trademark, patents, designs and plant breeders rights systems.
IPAustralia's advice on the registrability of trademarks.
Search International trademarks with the ROMARIN database. It contains all the trademarks recorded under the Madrid system. Updated daily with the marks in force, under examination or expired in the last six months.
USPTO is the United States Patent and Trademark Office.
The UK has it's trademark system administered by the Intellectual Property Office.
The Intellectual Property Office has an online trademark search facility available at http://www.ipo.gov.uk/tm/t-find/t-find-text/
The New Zealand trademarks system is administered by the Intellectual Property Office.
The New Zealand online trademark search is available at http://www.iponz.govt.nz/cms/trade-marks