L.CCR.4 — that's the 4th College and Career Readiness anchor standard within the Language strand of the Common Core State Standards (CCSS) for ELA/Literacy — says:
Determine or clarify the meaning of unknown and multiple-meaning words and phrases by using context clues, analyzing meaningful word parts, and consulting general and specialized reference materials, as appropriate.
Here's the short version: college and career ready (CCR) people are good word figure-outers.
L.CCR.4, the first in a “Vocabulary Acquisition and Use” trio, is all about one central question: What do you do when you encounter words you don't know?
Within the anchor standard, there are three main strategies for figuring out word meanings.
Using context clues
CCR people need to know how to gather information about an unfamiliar word using the words around it. This is, by far, one of the quickest ways to determine the meaning of an unfamiliar word, but it's also not always a sufficient strategy, especially in texts with lots of unfamiliar words. In texts like that, it's best to verify the inferred meaning with an external reference, if possible.
Personally, I think the best way to teach using context clues during modeled reading of grade-appropriate complex texts.
Using word parts
Suffixes, prefixes, and word roots — booyah! The grade-specific versions of L.CCR.4 have kids doing a lot of work with word parts even in the earliest grades; by the time 5th grade comes, they're familiar with some basic Greek and Latin roots; by 12th grade, they are beginning to use patterns of word changes to infer more nuanced levels of meaning (e.g., analyze, analysis, analytical).
Dictionaries, glossaries, thesauruses, etymologies — fun stuff! CCR people need to know how to use reference materials, both in print and online, to gain an understanding of words they don't know or to clarify inferences made using the two methods described above.
I also think they need to have a grasp of the strengths and limitations of various reference materials. For example, a thesaurus can help you get an idea of a word through reading about similar words, but it's also not as precise as a dictionary.