Start with noun and verbs phrases, which are the most concrete and easiest to sort into categories. Give your student several cards with words or short phrases on them. You might give her phrase cards that read 'the girl," "the duck" and "the boy," to combine with "ran" "slept" and "ate." Have her assemble them into simple sentences. If you give her the sentences, instead of inviting her to create them, she cannot experiment with changing the verbs.
Introduce the noun shapes. Explain that the triangle is solid and black like a pyramid because nouns are often solid, real things. Invite your student to place the triangles under the nouns in his phrases. If he changes his nouns, have him pair his new nouns with additional triangles under the original to demonstrate that many nouns work with the same verb.
Explain that the red circle is for verbs. Show your student that it looks like a red ball because verbs add movement and energy to her sentence. Invite her to place it under the verbs to show which words give her sentence energy. She should now have both nouns and verbs marked with shapes.
Invite your student to expand the phrase. Show him that he can enhance it by adding adjectives, for example. Bring out the dark blue triangle and set it next to the black triangle to show how the adjective modifies, or changes, the noun. Repeat this process with different adjectives. Add a triangle and word pair in a column under the original adjective-shape pair to show that many different adjectives can modify the same noun.
Introduce the other parts of speech in a similar fashion. With each new concept, pair a word card with the corresponding Montessori shape. These include articles (small, light blue triangle), pronouns (large purple triangle), adverbs (small orange circle), conjunctions (small pink bar), prepositions (green crescent) and interjections (gold triangle with a circle on top). Reinforce that the parts of speech are categories that help you understand the speaker's meaning.