Read the pre-requisites. Many of these courses have a strict set of requirements. For example, you might need to be of a certain age, possess a certain educational level or meet any other set of requirements as delineated by your particular program. Make sure you meet the requirements before you decide to apply.
Complete the application. Read the instructions with a high level of detail. The assessor will look at your ability to completely follow directions along with your resume and other experiences. Make sure to proofread your application multiple times before sending it in. Attach any materials required in the directions. Also, if some attachments claim to be optional, you should seriously try to get those parts of the application filled out to optimize your chances. This will put you a step above other candidates.
Attend the interview. If you receive an interview, be sure to show up on time and dress professionally. Conduct yourself in a business-like manner to optimize your chances of success. Start the interview with solid eye contact and a firm handshake.