After the corn has grown to about ten inches high, using a hoe or hand trowel, pull up some soil from the growing mound around the base of the corn stalks. The corn should not be buried entirely, it's upper half should be above the soil that has been mounded around it's stems. The corn will send roots into the mounded soil to hold it steady and upright in the wind.
After mounding soil around the base of the corn stalks sow about a dozen pole bean seeds in a ring pattern six inches outside the corn stalks. Push the bean seeds about an inch under the soil and firm the ground above them by patting it down with your hand. Water the growing mound well. The beans will usually begin to sprout in about 7-14 days.
About a week after the beans sprout, sow six or seven squash seeds in a ring about 12-15" outside the beans. Push the squash seeds about an inch under the soil and firm the ground above them by patting it down with your hand. The squash seeds will sprout in about a week.