Disclaimer: I am no expert! You will probably get much better answers than mine, but I'll give it a go...
1. Make sure they are strong in the basic parts of speech. You will beat your head bloody trying to teach them things in English if they have no knowledge base in their own language. If you don't teach the basics in Spanish, it doesn't really matter, so long as they understand what the words mean (noun, verb, etc.)
2. Teach affixes. I would start with prefixes. Make sure to let them know some simply have to be memorized because there exists no "logical" or intuitive connections; for example, the suffix "-ly" in English, generally creating an adverb, corresponds to the suffix "-mente" in Spanish, also creating an adverb. They just have to remember it!
3. Help them with visual cues for things which may look similar but sound different: "-cion" in Spanish corresponds to "-tion" in English.
4. Dig, dig, dig yourself! Depending on their ethnic background (guessing Mexican, as you hail from CA), familiarize yourself with their colloquial expressions and words and find a way to draw out word origins and meanings. Here's an example from my side of the cow patty: We have a good sized Puerto Rican population. The colloquial word for an orange is "china" (pronounced "cheena"). Standard Spanish for orange is "naranja". Where did this "china" word come from? Logically, the country. Southeast Asia is the origin of oranges, hence the moniker. The more you learn about their colloquialisms, the more dots you'll be able to do number 5:
5. Connect the dots. Throw in as many different languages and connections as you can. Encourage questions and mistakes, and use them to make more connections.
That's all I've got off the top of my head. I'm sure others will have some much better ideas! Buena suerte! :0)
