Develop a standard set of criteria that will help you evaluate if the students have achieved the learning objectives. Each criterion should describe the expected results on a hierarchical scale from basic skill to advanced critical thinking. The assessment criteria should be easily measurable and independent from the specific caracteristics of any given project/unit.
Ask yourself these questions:
How will you evaluate the objectives that were identified?
Have students practiced what you are asking them to do for evaluation?
You will need to gather some evidence that students accomplished what expected by the lesson plan. Tipically his is done by collecting students' work and assessing it using a grading rubric based on lesson objectives. Additionally, you could quiz students on concepts and problems that have been addressed by the lesson plan.
Be sure to give students the opportunity to practice what you will be assessing them on.