Choose a topic to base your theme on that interests your students, or a theme that focuses on a specific topic that you wish to instill. For example, if you wish to instill an understanding of the summer season in your students, or if your students express an interest in farm animals, use these topics as as your theme.
Set goals and objectives for the thematic unit. Decide what it is that you want your students to learn about the chosen theme and how the theme can be brought across the curriculum to teach content specific skills and concepts. For example, if you are teaching about the summer, what do you want students to learn about the season and how can elements of the season be used to teach math, reading and science skills and concepts.
Decide how to introduce your students to the selected theme. For example, when teaching a unit on farm animals, reading a book that relates to farm animals introduces the unit in an engaging way and integrates English-Language Arts.
Design lessons and activities that both teach about the theme and content specific skills and topics in a way that your students can relate to. If you're teaching addition during a summer-themed unit, use pictures of suns as manipulatives to teach the skill, or spread sunscreen on half a sheet of paper and leave the other half blank, set it in a window and observe the effects for a science activity.
Incorporate a culminating activity at the end of the unit to tie everything together, revisit the theme and increase comprehension of the unit. During a farm animal unit, take students on a field trip to a farm, or at the end of a beach-themed unit, take children to the beach or plan a beach day in the classroom.