Compound words are an important point in structural analysis because they can either stand alone or be combined to make a third word. A good way to help students with this concept is to play memory. Write half of several compound words on one card (so, "zoo" on one card and "keeper" on another), then turn them all upside-down. Have students take turns flipping them over; if two words make a compound word, the student gets a point. If not, he puts them back in their original position and it is another student's turn.
Affixes change the meaning of a word by attaching to the beginning (a prefix) or end (suffix) of that word. "Clearly" is a different word than "clear," and both are different than "unclear." A good activity is to write a root word on the board, then have students take turns coming up with changes that can be made to it by adding prefixes and suffixes. Encourage discussion as to what the new words are and how their meanings changed.
Read to your students, but occasionally stop to discuss the structural analysis. So, for early learners, you could say "he opened the..." then wait for the students to shout out "door." Next, you can discuss what letter "door" starts with and why it starts with that letter. What would happen if it started with a different letter? This will encourage children to think about the nature of word formation.
More-advanced students can learn words from context. A good activity for this is to write a sentence with a nonsensical word in it on the board. "The dog xarfed all night and I couldn't sleep a wink" is a good example. Kids will be able to quickly figure out what "xarfed" means, which will teach them the value of context in determining a word's meaning. This activity emphasizes the point that words do not occur in a vacuum.