Ask HN: Effective communication in the office?

Hi HN, I am working on some soft skills in the office, and this might seem dumb, but I am trying to figure out how to write requests and comments that are constructive and firm but not intrusive or abrasive. For example, a co-worker said they'd schedule a meeting for tomorrow, and I wanted to point it out to them that they made the meeting at the wrong time, so I said: "For the meeting, it looks like you scheduled it for today instead of tomorrow", and he responded a little coldly, so unsure how I came across. Another example is the way I ask for things. From a sentence today, "if you have some bandwidth, I was wondering if you could [do X because Y]" I needed the data by the next day but this person just came back from vacation and had a big backlog, so I wasn't sure how to convey that but also be respectful of their time. My boss needed the data for a presentation to his boss but it was a little unclear how important the data, so I sort of let it slide. I ended up getting the data anyway. Does anyone have guidelines, maybe books, or examples of converting common phrases to get the point across? Apologies if I am overanalyzing. Thanks for any help!