Cover them with a half inch of potting soil, place in a warm spot, and keep the soil moist. It may take a month for the seeds to sprout, so be patient. Citrus trees take many years to bear fruit, and most won't in your house, but sometimes they will bloom and the fragrance is wonderful. Date pits will grow into a five foot palm tree, if given proper care. Cover them with a half inch of potting soil, and keep them warm until they germinate.
Dates take even longer than citrus to sprout, sometimes up to three months.
Keep them cool in winter and re-pot every year. Sweet Potatoes make a pretty vine that looks great on a kitchen windowsill. As with the avocado, find a jar or glass and insert toothpicks to hold the sweet potato in place, the pointed end of the sweet potato down. Make sure that the end stays covered with water. You will see results fairly soon, and within a few weeks the vine should begin to fill out.