Smart people know that the key to clear communication is to:
Why you should not use: When you say "I could care less." it doesn't mean that you don't care. It means you have some level of caring.
What to use instead: I don't care.
Why you should not use: When you use "All I know is . . ." to start a sentence, you run the risk that the listener will take your words literally, and assume that you don't know anything else.
What to use instead: Here are the facts as I see them.
Why you should not use: When you start a sentence with "Needless to Say . . ." you are wasting everyone's time - yours and your listeners - by pointing out something that is obvious. If it is needless to say, then it should not be said.
What to use instead: Just say what you have to say, deleting the lead-in of "Needless to say . . ."
Why you should not use: When you say "It is what it is." you run the risk of appearing to be a lazy person who just wants to leave things as they are or who is not willing to give an opinion or to fix something.
What to use instead: "That is the situation." or "That is what I was told."
Why you should not use: To say "It was for the best." may not be true and it may just be offered in the conversation as the easy thing to say.
What to use instead: That's really unfortunate.