In order to avoid ruining the pattern, the transparent paper will allow you to change your pattern several times if necessary. You dont want to use your initial pattern because once you have cut it and adjusted it to your need; you wont be able to apply it for anything else. Having a ruler is another essential item. The smaller increments it shows, the better. While being extremely helpful, a ruler with measurements as small as 1/16th of an inch could be needed when pattern grading.
If measurements of 1/16th of an inch is not noticeable on your particular ruler, as long as it shows 1/8th of an inch a smart tip is to take a fine tipped pen to make tiny marks between each increment where your still able to tell where 1/16th of an inch will be. Tracing a pattern on the transparent paper will have to be done using markers or pencils so have them handy too. While markers are bold and unmistakable, pencils can be easily erased should you make a mistake while tracing your pattern. Tape is an additional thing that is helpful when grading your pattern, because you dont want your paper to slide if you are tracing your pattern. If you do not have tape, there is a risk of having to start all over should the pattern slip and be cut out wrong. Clear tape is great because it is see through so you dont have to worry about it blocking your view of anything.
When it comes to actually cutting your pattern out, a flat cutting surface will be required for accuracy. Regular cardboard will work great and is a terrific money saver as you can likely find some lying around the house, or find someone that has some they will give to you. You will also need pins to attach your pattern to your cutting work surface. It is also helpful to have an idea of what your measurements are should you be making something for yourself or the measurements of the person you are sewing for ahead of time so that you dont have to do a lot of math off the top of your head. Once you have these tools, you are prepared to grade your pattern.
One of the greatest approaches to find out about correct grading techniques is via reading pattern grading books. To get more particulars on Fashion Patterns by Coni, see them at their web site, http://www.fashionpatterns.com/.