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!