Using big, impressive sounding words rather than smaller, common ones can leave listeners with the impression that you're pompous and pretentious.

The fix, in this case, is a big dose of humility. 

These are words or sounds you insert into sentences when you're pausing to think. Examples: 'um', 'like'. Too much of these will annoy your audience.

When you simply pause in silence, rather than trying to fill the thinking space with the hiccup, you end up sounding wise and like you're choosing your words carefully.

They turn statements into questions: a raise of pitch at the end of the sentence or an actual phrase, like "........., you know?" or "............, eh?" They indicate that you're not confident in your communication skills.

Ask a specific question instead,  such as "Does that make sense so far?"

These are attempts to disguise ugly facts as abstractions. Examples: using "development opportunity" when you mean "drudgery," or saying "rightsizing" when you mean "firing people." They mark you as a coward.

You'll get more respect and credibility in the long run for telling unpleasant truths than for pleasant-sounding lies.

This is what people do when they feel socially obligated to apologize but they aren't really sorry. This ends up being even more offensive. Example: "I'm sorry if anybody was offended." 

If you can't apologize from the heart, don't bother, because you're not really apologizing.

This consists of blurting out a stream of facts or observations before finding out which ones (if any) might actually be of interest to the listener.

To avoid this, ask questions, respond to comments, figure out what's needed, and only then trot out facts and observations that are immediately relevant.