After you have completed your application, you can expect to be called in for an audition and/or interview. Some art and design subjects may also ask that you produce a portfolio. It is best to check BEFORE you apply what the next steps might entail so that you are available and prepared.
Each institution and each subject will expect something different from their portfolio, interview or audition procedure- be sure to check this out.
That said, below we have put together some more general advice to help you on your way.