Study the state standards. It is imperative that you familiarize yourself with the first grade state standards for Language Arts, Math, Science and Social Studies. You can teach in the order of the standards, or teach multiple standards per lesson. If you are just starting out, try to keep it simple. Focus on one or two standards and benchmarks and work from there.
Research lesson plans for first graders. There are immense resources online or talk to your fellow co-workers. Teachers should work together and learn from one another. If the state standard focuses on vocabulary then create vocabulary lists that build off a short story from the lesson. If your school utilizes a statewide curriculum then use the text provided to serve as a framework for your lesson plans.
Select the standards and benchmarks that you will be focusing on for the day or the week (depending on the length of lesson). Once you choose what you will be teaching, begin thinking of how you will assess that particular skill when the lesson is complete.
Create an assessment that will accurately demonstrate whether or not the first graders reached the skills from the standards. Assessments can be tests, classroom observations, class projects, homework, papers, etc.; whatever you feel shows the ability of the student.
Write your lesson plan. Begin stating the standards you will be using. Define the objective of the lesson plan in your own words. Ensure that you have ample time and materials to deliver the lesson. Describe the exact procedures you will take during your lesson and explain how you will be teaching the standards through this procedure. Conclude the lesson plan with an assessment that determines whether or not students achieved the skills as outlined in the standards and objective.
Print out the lesson and save it in a binder. These lesson plans can be reused next year or serve as a reference later on.