CV and Covering Letters
CV's and what to put in them: www.nationalcareers.service.gov.uk/get-a-job/cv-sections Here are two I have put together using the templates.
Covering letters: www.nationalcareers.service.gov.uk/get-a-job/covering-letter
Preparation for interviews
Your interview may include aptitude tests or psychometric tests - in order to prepare you for these try out some examples. You will need to do these for the Armed Forces, Engineering and Technology roles but most employers will ask you at one stage or another.