We use Rocket.Chat in our daily routine. We expect you to use it while you are working. Make sure to add #important to your favorites, or check it regularly. Company announcements are usually made there.
Please do not say just "Hello" in chat. It is as if you called someone on the phone and said "Hi!" and then put them on hold!
You are trying to be polite by not jumping right into the request, like you would do in person or on the phone. But Chat is neither of those things. Typing is much slower than talking. Instead of being polite, you are just making the other person wait for you to phrase your question, which is lost productivity.
Asking your question before getting a reply allows for asynchronous communication. If the other party is away, and you leave before they come back, they can still answer your question, instead of just staring at a "Hello" and wondering what they missed.
Audios are not searchable. Make sure that when you use audio it's short and given a context around, so people can find it if they use the search. Audios should not convey more than one topic or task. You can't break an audio into multiple pieces if you need to refer back to a specific point in time.
When you ask someone to help you with something, but this person takes too long to answer, and you end up finding a solution somewhere else, let them know. Many times the person didn't answer right away and will try to find the solution before they tell you they are looking for one, so they can give you a complete answer (and an asynchronous one). So as a gratitude token towards them possibly finding a solution, let them know they don't need to worry about it anymore.
Even on DMs, if you need someone's attention immediately, mention them so they will see a red badge besides the room name. Don't overuse it, though. Mentioning people in every DM will make it useless and people may start ignoring it at all.