Present your child with a list of "common words." Examples of these words might include "here," "through," "there," "everywhere" and "another." These words have a high frequency in spoken and written language, so emphasizing them will build a strong foundation for your third grader. Have your child read the list of words, talking about what each one means. Next, find a short story or poem in which these words are used in a simple context. Read through the story, assisting your child with any difficult words, and then talk about what happened in the story to encourage not simply reading fluency, but also reading comprehension.
Have your third grader read from a children's book or magazine. As they read, encourage them to circle or underline the words that they do not know. Once they have read one paragraph, go through each sentence, examining the unknown words. Rather than telling your child the meaning of the word, have him try and discover the meaning through contextual evidence. Ask him what the rest of the sentence says, what he thinks the word might mean, and whether the word appears or sounds like any other words he knows. Work through the paragraph, increasing your child's vocabulary and teaching him how to define words simply by using the context and words he already knows.
Solidify your child's existing vocabulary, and encourage her to discover new words through writing. Have your child write a short story about a subject of her choice. When she is finished writing, have them read it aloud to you. Go through the story identifying various words and replacing them with synonyms. Write the story again with the new set of words and have your child read it aloud once more. Discuss the new words and how they might change or enhance meaning. Your child will improve her existing skills while increasing her ability to read and write new words.
Whether your child struggles with reading, or is simply more interested in playing video games, making reading a special event is a way to encourage his reading ability and frequency. Plan trips to the local library and help your child register for a library card. Help him select books of interest and read with him. You can even create a "reading corner" in your home that is a special place for your child to read his books. Have him help decorate the corner and organize his books in the space.