Another way to avoid locking a file is to open it as Read Only.
In addition to closing the file when you are done, there's another way to avoid locking files: Open them as Read Only. You should do this when you don't need to change the file at all but you do need to read it or refer to it. When the file opens, you won't be able to make changes, of course. However, others will still be able to edit the file when you have it open as Read Only, so you won't lock them out.