Use tentative language - You can always be wrong, and you should acknowledge that in how you communicate:
Bad: "Your code isn't performant."
Good: "I think this code may have performance issues."
Body language matters - Communication isn't only the words you say or write, it's also how you express with your face and body. This is something that is biologically wired into humans: Put your entire self into it when you are communicating, especially when you're listening! This is covered more in the part of this course about deep listening.
No leading "hello" for digital communication - When asking for help digitally, don't do a greeting and then wait for a response greeting before jumping into your ask: Just attach your ask from the get-go. Software is all about efficiency and waiting for this round trip makes things less efficient. For more advice around asking for help effectively, here's our in-depth video about it.
Lead with the core point - Think of a "tldr" when it comes to long articles. This also applies to how you talk: Start with the main idea, and then go into the details. When you start by going into the weeds (very common for earlier-in-career engineers), it's very easy for people to be uninterested or get lost in what you're saying. For an example of how this applies to technical writing, check out this Q&A from a Meta engineer about it.