When working through the questions, quite often you will answer by gut instinct. Later, you may be reviewing the answers and end up double-guessing yourself.
More often than not, the first answer you put in is the correct one.
Don't get caught up with convoluted "possible" answers if you are not sure. Go with the gut instinct.
Also, do as many sample exams as you possibly can, under test conditions (lock yourself away for the alloted time, with the required equipment, and no distractions). Sample exams will illustrate your areas of deficiency, and give you a study strategy. Additionally, many of the questions you get will be identical to the actual exam questions.
As others have stated, RTFQ. Analyse EVERY single word in the question. For example, WILL and MAY have two specific and different definitions. You WILL get other questions with ambiguous words which are not ambiguous at all. You MAY misread them, while concentrating on the actual aviation part of the question.
If you are continuing on to CPL, it is worth getting started on the CPL exams while your PPL exam knowledge is still fresh. For most of the CPL exams, you will find that 80% or so of the information has been covered in the PPL. The CPL exams will ask you tougher questions, and require a more detailed level of knowledge, and also introduce other elements, but you'll be surprised at how much you will have already covered in the PPL.
Don't stress. If you have prepared properly, at the end of the PPL exam, you will likely be thinking that it really wasn't as difficult as you thought it would be.
Good luck!