There are lots of guides on how to make a FOI request. One of the best is Foiman's at http://www.foiman.com/resources/foiguide1. The ICO guidance is ok too.
But if you are not experienced at using FOI, how do you work out whether the gobbledygook you have received is a good or a bad answer?
I am still irked at how few people ask for internal reviews (and where organisations do not have someone independent and senior in the organisation assessing the internal review, I cannot see how they can have much value), and how rarely people go to the ICO, let alone the Tribunal.
So, I intend to write a series of posts, going through the exemptions, roughly in order of how often they are used, so requestors can learn to spot a bullshit reply. This is not meant for seasoned requestors, but for relative beginners or infrequent requestors.
Do read Paul's guide and the others that he links to - these are excellent starting points.