Here's one that will keep you up nights.
Diction is defined "Degree of clarity and distinctness of pronunciation in speech.."
The words most people screw up when it comes to diction is almost anything that starts with "tr" or "dr". Test this on yourself, you will probably fail the test.
Say the word "truck".
Now analyze the way you said it. Did you say "chuh-ruck"? Most likely you did. There is no "chuh" in "truck". The proper pronunciation is "terr-ruck". "Church" is pronounced with a "chuh". "Truck" is not.
Say the word "drive".
Did you said "juh-ry-vuh" (said slowly that is how it comes out most of the time)? You probably did. It's "derr-ry-vuh". There is no "juh" anywhere in the word "drive".
Say "try". Did you put a "chuh" in it? You probably did. It's not "chuh-ry", it's "terr-ry".
When you finally master eliminating "chuh"'s and "juh"'s, you'll then start spotting all the people who say words incorrectly. Then you'll start noticing how many actors in television and movies say words incorrectly. Then you'll wish you never read this article. 😉