New writers sometimes hear that a thesaurus is an excellent way to punch up their prose. What can be easier? Just remove your tired, jaded word and replace it with one of its scintillating synonyms!
Except.... "synonym" doesn't mean 'exact match.' And things get even fuzzier when you get out to the 'related words.'
For instance, imagine Annie Q. Writer has the following sentence in her WIP:
He had flashing eyes, black hair, and a rapier
"Wait!" cries Annie Q.'s critique partner. "That's a cliche! fix it!"
So AQ diligently goes to her Roget's thesaurus (I've had mine since 5th grade...it's on the edge of death) and looks up rapier.... well, the thesaurus mentions "Claymore" as a synonym. So Annie plugs it in.
Unfortunately, a Claymore with would be huge, heavy, and cleave people in two, while a rapier wit would be darting and stinging. The change of word results in a change of sword which COMPLETELY changes the meaning.
Last night I also noticed that my trusty old thesaurus (I hardly use it these days, actually, except for entertainment value) also claims that "lumbering" and "hobbling" are equivalent.
But...no. Great Aunt Mary is currently hobbling do to a fall. She's a tiny bird of a woman and could never, ever lumber, no matter how hard she tried.
A dictionary is like a pair of goggles. It can help cut down on accidents from your thesaurus. But it's no substitute for a good word sense.
No one is born with word sense. You get it by reading great writers who use words well. The more you read, the more you understand the fine flavors of every word. (Look up the ones you don't know!)
So park the thesaurus on the shelf for a while and head to the library or bookstore. Read all those excellent novels you've been putting off. Then, when you come back, you'll be able to use your tools more efficiently.