It takes time to improve your language skills. You can, however, make some small changes that can have major impacts on your score. In the writing section, it could be to be more aware of the transitions between paragraphs and having a logical order in the text as a whole.
The reading section has a lot of technical, boring stuff in it. I remember one of mine that was about geology that almost put me to sleep. The key is to catch the most important points of the text instead of trying to understand and remember the whole thing. You don't have to know all the terminology of the subject in the text (I don't know anything about geology). Ask yourself: why did the author write this paragraph? (or: what is the point of the paragraph?)
I don't think you need a great vocabulary to get a good score on the TOEFL. I didn't study for the test - or even know what was on it - when I entered the testing centre and I would say that my vocabulary is pretty mediocre.