If you are spending too much time for initial questions, then you have less time to answer the last few questions. Spend time equally. The first few questions matter, because if you make many careless mistakes in the beginning itself, then you will have tough time reaching the actual level you are capable of. So first few questions are stressed to warn that you should not make careless mistakes, you should be more cautious and it doesn't mean that you should spend more time to solve them. Your focus during preparation should be on reducing careless mistakes to help you get your maximum ability gauged by the test. Scaled score depends on the overall performance. Improving your content knowledge is the best way to perform well. The difference between a 750 level test taker and a 650 level test taker is that a 750 level test taker will be able to solve the first 10 questions easily and quickly, while a 650 level test may be able to solve them with more time, but at the end you will be where you started because with less time and more difficult questions to answer you will eventually fail. So its all about content knowledge and not about which part of the test is important. Follow a timing strategy and don't set any priority to any part of the test.

I second the previous response by sam2304. If you are spending too much time in getting the first few questions right and then are ending up rushing through the other questions then it might affect your score in the wrong way. If you have a few mock tests to test with, getting consecutive questions wrong does tend to have an effect on the score. The first 5-6 questions can be attended to with care provided you are sure of making up on the lost time on the next 6-8 questions.