Say why you are contacting them right away!
I always tell people to stop saying just “Hi” and waiting for a response when you message someone. It is a total waste of time. Instead, say what you need from them right away.
The recipient may be busy and may not want to start a conversation at that moment. But if you tell them what you need right away, there’s a good chance that they might be able to quickly answer you and move on. That saves a lot of time for you.
This rule has become more relevant now because most people are working from home these days and everyone communicates through chat apps. People could be busy with many things, so if you contact someone for some information, don’t just say “Hi”, instead ask for the information.
Read the discussion on this on HackerNews.