When it comes to editing your own writing, you can use whatever marks that you'd like to use on your paper that you find you can understand. However, there are a set of proofreading marks that people use when proofreading or even grading papers. Not everybody uses all of the marks. It is extremely likely that you will not use all of the marks yourself, but it is good to know some of the basic marks. Knowing them makes it quicker for you to be able to find what you are wanting to change in your current draft of your play.
Capitalization can be a big thing when you are wanting to make sure the play is written in a correct format for submission or just for others to clearly understand the play. When you come across a word that is lowercase, but it should be capitalized, you write three lines underneat the first letter. It kind of looks like a little sandwich sitting under the letter. That way you know that the letter was meant to be capitalized. For lowercase, you can do the same thing to a capital letter, but most likely outside of the margin, you will write "lc" for lowercase. If you prefer for yourself, you can write lc near the letter that should be lowercase.
When something needs to be inserted, a caret is drawn underneath where the symbol should go if it is something like a comma or a period, and the symbol is put in the space of the caret. If the symbol is somethign like an apostrophe, the caret is drawn above and it points down to where the symbol shoujld go. If there is an improper space in a word, then the way to show that it needs to be corrected is to draw a little curve over and under the part where the incorrect space is. If a space needs to be inserted, plus a number sign (now commonly known as a hashtag, and formally known as an octothorpe) above where the space should go. Sometimes the caret is used along with the number sign in order to show where the space should go.
The mark of "sp" can be confusing at first. It is used for two different reasons. One is an indication to spell out a number or an abbreviation. Perhaps you have something like "5" in your draft, but it should be "five." That is one instance where it is used. Maybe you want a character to actually say the words, "National Association for Colored People," but you wrote NAACP. This would be another place where "sp" would be used and the term needing to be spelled out would be circled. The "sp" might be in the left margin or it might be above the circled word. Then "sp" can also be used for when something is misspelled. The word will be circled and "sp" will be in the left margin or above it.
The very last proofreading mark that I am going to mention is the one for deleting a word (or sometimes a single letter, though it is usually not used that way). A line is drawn through the word and then right above the word, still attached to the line, it looks like a cursive small e, or just a little loop in the line. That means the word should be deleted.
Having knowledge of these few proofreading marks will make editing your play easier on you. You won't have to write out every small detail of editing. If you want to learn more about proofreading marks, there are plenty of resources found online. You just have to search for them and they will come up in your search results on any search engine.
If you enjoy my content, please consider becoming one one of my
patrons through Patreon at
https://www.patreon.com/TheatreGeek where I will be sharing more in depth content, answering your questions, sharing which types of software I use and how to find them, and more. By becoming my patron, you allow me to create more content about theatre and more theatrical content.