SEO, keywords and traffic

I have a passion site reviewing cars. I do all the writing and would like more traffic to the site. I am looking for someone who can advise what I can do and also implement necessary actions to improve the site and get it ranking on Google. Treat me as if I know nothing and, in your application, please state what action you think would be best and what I would do and what you would do. Specify if you think it needs to be ongoing or just a once off (for the first site). Further to this project I have other sites so, for the right person, more work could follow.