Pattern grading is a whole different area to pattern cutting. These days grading patterns are a lot easier done because computer grading is very advanced and widely used.
This video is a quick tutorial into manually grading a pattern, up or down a size. When you are resizing a pattern, you need to bear in mind what the total increase or decrease is that you want, because it might affect the total difference. For example, if you are increasing the arm whole length by slashing across the cross front, that increase will contribute to your total body length increase. Always remeasure and double check the results. Hope this helps!
If there are any questions or maybe I have missed something out in the video please feel free to get in touch. Thanks :)