I can't tell you how important it is to study word groups.
When you come across a word such as "slope," for example, look up other similar words.
Maybe you'll find words like:
incline, slant, hill, gradient
This person is scaling an extremely steep incline!
These word groups are SO helpful on the TOEFL because this test loves to use synonyms in the answer choices. If you didn't know that slope was also an incline, then you might disregard this answer choice and select the wrong answer.
If you want to learn word groupings, simply look up any word on a thesaurus.
My favorite thesaurus these days is here.
Now that you know how to go uphill, let's go down!
Explore the synonyms of holes with me in this video: