Literally vs figuratively
This is an endorsement I read the other day: “Debbie Bermont’s seminar - How To Get A Business Success Mindset Like Oprah And Bill Gates With One Easy Formula - quite literally knocked me off my chair!"
Really? You suddenly found yourself on the floor, looking up at your chair, possibly with minor injuries? Or did you mean figuratively? Generally if you don't indicate which but it sounds unlikely that it was literally, we will assume it was figuratively.
Complement vs. Compliment
"This scarf will compliment any dress." So it's going to speak and say, "Wow, you are some dress!" Compliment means to say something nice about something. Complement means to go with or add to. Likewise, complimentary means free, complementary means associated with or in tune with.
Peek vs. peak
I have been surprised to see these confused more and more often. Peek means to take a sneaky look at something. Peak means the top. Unless you are characterizing a mountaintop as somehow untrustworty, it's "sneak peek," not "sneak peak."
Farther vs. further
As the first part of the word suggests, farther is about distance. "It's not much farther to the pub." Further refers to time or degree. "If we take the argument one step further..." or "I will make further phone calls to check on this."
Begs the question
I'm not even going to try to explain this one. Just be aware that it doesn't mean the same as "raises the question," which is what you should say when that's what you mean.
Principal vs. principle
This is another one I'm seeing more often. The principal is the main or most important (including the school Principal). Principle is an ideal or code of conduct.
If it's unique it's one of a kind. It can't be very unique. Kind of like being pregnant.
Finally, my 7th grade teacher Mrs McKinley would be proud to hear me say it: If in doubt, look it up! With the internet it takes even less time. Which reminds me,less is used with anything that can't be counted or doesn't have a plural (less money, less time, less trouble); fewer applies to anything in the plural (fewer people, newspapers, hours, etc.). Occasionally this gets tricky as in "It will take you six hours or less" because what's implied is "less time."