If you see a picture of the word you are saying, point it out. If there is an action mentioned, mimic it. Sing whenever possible. This both entertains the child, and helps them to learn the names of the parts of the body. Pointing to a cow in the picture when a cow is mentioned in the rhyme helps to associate the picture and the sound of the word, also expanding the child's vocabulary.
Every line has something to do.
Stand up and act it out with the child. If these motions seem contrived or awkward for you, come up with your own. The point is to amuse and delight your own child, and you will know best what works for the two of you. Using movement or hand patterns, as in Eensy Weensy Spider , also give the child a chance to imitate you, work physically with you, and practice their motor skills. You may find your child imitating your gestures very early on, especially if you make a ritual out of using the same gestures with the same words for certain rhymes.