This one-page document has taken me several years to develop. It is the result of much trial and error in correcting student work in my Spanish classes.
At first, I used to write in all the corrections out in words and phrases, which took forever and was very repetitive. Then I developed a code from A to Z with all the most common student errors, but without trying to make the letters correspond in any way to the correction they were indicating.
Over the past year, I've revised the document several times to get it to a place where all common errors are present and all letters of the alphabet correspond in an way that is easy to remember (which wasn't easy). Each letter now has a logical connection to the correction. After using the code for one batch of projects or essays, I'm sure you'll find that you no longer need to use the document because you'll have it all memorized.
The document includes an example of each error and an example of the correction that should be made, so that students have an idea of what they did wrong.
I print this page off on cardstock and holepunch it for each of my upper-level Spanish students (grades 10th-12th) and have them put it at the front of their binders at the beginning of the year. Then, each time I hand back corrected work. I ask them to take a few minutes to look over the corrections, noticing patterns of errors that they make over and over again.
I also usually allow students to make corrections on written work that they've done. This corrections code allows them to figure out for themselves what they should have written and promotes growth in their ability to recognize the errors next time.
I hope this page helps you!