"Keep it simple" when you develop preschool homeschool lessons. At this stage, you are aiming for quality, not quantity! They learn quickly and will continue to learn for the rest of their lives.
I am not suggesting NOT to teach but rather to be mindful of the relationship you can build during this time and not hinder that through piling so much information upon them with your preschool curriculum ideas.
That answer will vary from place to place and from family to family. But, I think most of us can agree on some basic subjects that should be included in a preschool program such as Bible, Character Education, Manners, Citizenship, Math, Phonics and Reading, History or Social Studies, and Science. Other subjects can be included once the basics are in place.
I use relevant themes or units of study in creating our homeschool preschool curriculum program.
Once you determine what your child needs to learn you can develop his/her lessons with inexpensive preschool materials that you purchase or make on your own. As you teach your child keep in mind that you are laying a foundation upon which future studies will be added.