Even if you never pick up a calculator, there are a couple of steps in the land of Knitting Math that we all seem to forget. Mostly they involve writing down the stuff we did and changed, as it's different from what the pattern said. Two years later, when you decide to make this project again, you'll really want to know what the heck you did!
Let's say you did some knitting math to place your decreases evenly, which your pattern asked you to do. Well, if the pattern doesn't specify how often to decrease and you did the math on your calculator, you know what to do for your decrease row. But if you take a little post-it note and stick it to the pattern, all the better.
Modify the sleeve length? Another post-it. Modify the gauge or change the yarn? Yep, more post-its.
Why all the post-its? Because if you knit past your changes and turn out not to like them, you'll rip back, and change it again. Then you can peel the first note and replace it with what change you liked better. This way you're not writing directly on the pattern. When you finish the garment, then you can take all the post-its and write out one final "change sheet". Make a little highlighter dot on your pattern every time you need to look at the change sheet for the next time you make the project. And of course, place a photo of the finished piece on the change sheet, or at least keep one with the pattern.
It might look like this: Change Sheet for Emma Jumper
Yarn: Used Cascade Rustic instead, total of 4 hanks
Needle: Used US 8
Cast - on: liked cable cast-on better, stayed with it
Length: found the original length too long for Jane (5 yrs old), and shortened it to 12" before the decrease
Decreases: k3, k2tog
Finishing: Finished by single-crocheting the V-neck bind-offs and the armhole for a smoother look.
Remember, the Change Sheet only represents what you did differently. It doesn't have to include anything you did the way the pattern suggests, just the changes. Paper clip this to the original pattern, and some day, (just long enough for you to not remember what you did differently), it will be there to remind you. Or it can remind your dear friend, who wants to borrow the pattern once they see the beautiful work you did.
This will feel silly until you go back to a pattern you never thought you'd use again. But you will use it again, because as knitters, our comfort zones move around. Let's say you didn't like all the cable work in a pattern. By the end of next year, you may suddenly want the challenge. What if you got through a colorwork pattern by the skin of your teeth, and are sure that's the end of colorwork for you? Well, in five years, you may LOVE colorwork. (Stranger things have happened.) Trust me on this. Making up a change sheet can't hurt you, it can only help you. There are so many patterns I've changed and didn't make a change sheet, and now I kick myself when I go back to them! Learn from my mistakes.