My advice, as someone who sat 3 times....
1) Accept that with the time pressures, you might not answer all the questions on some sections. Its better to miss 1 or 2 at the end, and use that time getting more questions from the start right. I did this on QR one year, still got like 800
2) Learn the basic techniques for each section. For example:
-With QR, theres the same set of basic calculations....working with percentages, timings etc so get familiar with those kinds in practice
-Decision analysis is all about absolute precision. The key mistakes i found i made were that when I wrote out the code, whenever i chose the wrong sentence it was because the one i chose was missing a word from the code, or the code had an extra word i didnt take into account. BE VERY PRECISE and you should be fine.
-AR is just....well, AR. I did start getting a lot better at spotting the patterns in the end....i'd try and spot the pattern on the first one from the section of 5, then you can answer the actual questions in seconds.
3) Understand WHY your errors are errors. Check the descriptions in the answer sections of the book/webpage you are using....you never know, something similar may pop up and this could save you valuable points!