Arguably one of the most important parts of editing is tact. Friendships and partnerships are made and broken, not by what is said, but HOW. As a beta, it is necessary to remember that we should critique, rather than criticize. What’s the difference? A critique is constructive, while criticism tends to be vague, insulting opinion.
Why is tact important?
Tact is important to master for two main reasons. The first and probably most substantial is that tact allows you to give comments in such a way that the author is likely to hear them. Comments that are rough or insulting generally are written off by the author as a personal attack, rather than a true statement about their work. They will then assume that whatever you have to say is worthless and untrue because you are just being mean. If your author does not hear your words, then why go through the trouble of editing in the first place?
I hope that these help you improve your etiting style in a way that benefits you and the people you edit for. Again, if you have any other ideas, please comment.