I am currently doing my first module which consists of GNAV, MET, Mass and Balance and POF. With subjects such as Nav and M&B I find that by continually doing as many worked examples and exam type questions as possible really helps to get what you should be doing into your head.
As for Met, the OAT CD ROM is a great interactive tool and has proven invaluable (to both me and those I know who have used it to pass the exam). As for POF, its a bit of a wordy subject which can be a bit confusing. I find learning it through various diagrams and how these interact beats trying to manipulate a load of jargon which was best left in the physics classroom at school!