Take an official IELTS practice test from the British Council.  This test is free and you do not need to register for anything to take it.

You can also take a free 10 hour online preparation course through the British Council, but this test is the same as the practice test linked above.  If you register for the IELTS through the British Council website, you will get a 30 hour online preparation course with two practice tests, video tips and examples.  You can also purchase the full 120 hour online course with even more great material.  Try the free preparation course here, you can read about the different courses on this page.

You can fine 12 more free practice tests on IELTS-exam.net.  Read my tips as you do a few practice tests and as you get to know the exam your scores will start to improve!