It is fitting that you place this question in the educational philosophy group, because how you write a lesson plan as a teacher depends quite a bit on your philosophy.  Here is a common lesson plan structure that is pretty flexible.  I have added the into/through/beyond structure.

Standard/Objective

Choose a state standard, and the use that standard to create a specific objective.  Objectives need to be measurable.  For example, students are able to ____________ with 80% accuracy.

Into/Anticipatory Set

This part of the lesson is designed to activate prior knowledge.  There are many creative ways you can do so.  These include KWL charts (students record what they know about a topic, what they want to know and what they learned), videos and anticipation guides (where students respond to a set of opinion questions based on the content).

Through/ Direct Instruction, Guided and Independent Practice, Assessment

Direct instruction is where you teach the lesson directly.  It doesn’t actually have to be as direct as it sounds.  It’s just how you get the information across.  Popular methods are lecture, notes, Power Point presentations, and discovery.

Guided practice is where you allow the students to try to practice what you have taught them, but you are around to help them when they need it.  This is best done as classwork.

Independent practice is where students try the concept on their own.  This is usually homework.

Assessment is an ongoing process.  You are assessing at every step of the way, but this part of the lesson is the actual summative assessment.  It can take any form, as long as you are checking student mastery against the standard.

Beyond/Enrichment

You will always have students who master the material before others.  Provide them with enrichment opportunities such as creative projects, research and performance.