Many students, even at more advanced levels, "can't see the wood for the trees" and when reading, especially, but also when listening, they come across an unkown word tend to "panic". Students should be encouraged to analyse not only the type of word, i.e. verb, noun, etc., but also the context in which it appears in order to hazard a guess at its meaning. This is particularly true of English, a language in which over 80% of the words have at least two meanings.
Context! Context! Context!
In other words, if a student asks "What does bear mean?", a teacher may instinctively reply "It's a big, fat, furry animal that likes honey and hibernates in winter" (or words to that effect), and the unsuspecting student rushes off to apply that definiton to a text in which the word appears in the sentence "He can't bear the sight of blood." That is, of course, if we're not talking about the homophone bare.
An exception that proves the rule to the importance of context is that of idioms, which are often too obscure for students to usefully guess their meaning.