Make a colorful board for your child's bedroom that explains exactly what nouns are. At the top the board, print in colorful letters, "A noun is a person, place or thing." Fill in the board with pictures of various nouns, for example, your child's family (with each person's name written underneath their picture), trees, flowers, books, shoes, toys, food items, landmarks, etc. Help your child to see that the objects she looks at everyday are nouns by relating the concept to something she already knows.
Read together and have your child point out the nouns in each sentence. This doesn't have to be a formal practice; make it fun. Help your child feel like she's playing a game. Allow it to be a competition with other children (or between you and your child) so that whoever calls out the noun first wins. Each time a noun is called, ask, "Why is this a noun?" so that your child gets ample practice repeating that a noun is a person, place or thing.
Have your child and a group of his closest friends and/or siblings work together to embody a sentence. For example, for the sentence "We walked down the street.", have each child choose a word from the sentence they will represent; have them write their word on a large sheet of paper, affix it to string and hang the word around their neck. Then, have the students stand in a line so the sentence is in order. Test each person by saying, "Will the noun please step forward?" "Will the verb please step forward?" Keep repeating the game with new sentences.
Encourage your child to refer to herself as a noun. For example, "I am Margaret. I am a noun!" This will help your child understand that all people are nouns. Have your child refer to where she lives as a noun. For example, "This is our home. Its a noun!", or "We live in Chicago. We live in a noun!" This will help your child realize that all places are nouns. At dinnertime, tell your child she's eating nouns. When she plays with her toys, remind her she's playing with nouns. Help her to see that all things are nouns.