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: Effective Communication Guide [Part 3.2] - 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: Asking Effective Questions That Get Great Answers Quickly
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: "How to get more visibility on work?"