(1) farther vs. further. Both are comparative degrees of “far.” In today’s usage, farther is used to indicate physical distance; further for figurative distance. Examples: The exit is nine miles farther down the road. And furthermore, I don’t want to hear anything else about Google plus.
(2) fewer vs. less. Fewer refers to number, and less is the word for degree or quantity. A common misuse of these terms is often found at the checkout sign that states “this line for 10 items or less,” (which should say “10 items or fewer”).
(3) lie vs. lay. The best way to remember this is lie is to recline, whereas, lay is to place.