I think an effective grasp of vocabulary is one of the most important tools we can give our students. The better your vocabulary the better your reading fluency, comprehension and writing skills are. Some things I think we can do as teachers to encourage that knowledge in our students:
1) Don't refrain from using the BIG words. I know many teachers who edit themselves-they will say this test is "hard". I will say "difficult" or "challenging". The more often you use that higher-level vocab the more often you will hear it echoed back in your students' words.
2) Encourage your kids to ask when they don't know what a word means. I can read a sentence in a read-aloud and I expect the hands to go up because I know it's a new word for them. We work on strategies for figuring out the meaning, but I also think it's important that they understand that word before we move on.
3) Read to them above their grade level. I heard this in a training once and have used that activity ever since-I find it to be extremely effective. We always have a chapter book going as a read-aloud-we read a chapter or so daily and it's my favorite time of day. Not only are they exposed to that upper-level vocab, they really have to listen for comprehension-no pictures.
4) Systematically teach vocab words. We do a word-of-the-day and I print out pictures that illustrate the meaning of the word. We will also often complete a Frayer Model in their Vocabulary Journals (examples below). I can't tell you how many times I am reading and they recognize a word we learned as our daily vocab word-they get so excited-"that was one of our words!".
5) Reward them for using their new words. Granted it's not always correct-after explaining the meaning of "sarcastic" one year, I had a student who would refer to saying the opposite of what you mean with a different tone as "psychotic". But they are taking the risk and trying to apply what they've learned-that should be encouraged.
Here are some examples of the Frayer Model and how we use it for daily vocab lessons. Obviously some words work better than others, but I can read what they've written and automatically determine if they "get it". One of my favorites was for the word "devious"-the student wrote Santa as a non-example-he came up with that purely on his own and obviously it demonstrated he understood the meaning.