Meaningful assessment begins with YOU.
As faculty, you are familiar with giving students assignments, exams, and other learning assessments. Similarly, assessment is intended to help faculty, departments, and institutions gain feedback on effectiveness, depth of knowledge, and outcomes. All of which strengthen practice, aide retention, and communicate quality.
Assessment as a cycle.
Assessment is a cyclical process that is only useful if you analyze the data you obtain to make decisions. These decisions are often centered around pedagogy, but do impact curricular offerings, student support, and institutional allocation.
Assessment is a process, not an outcome!

Where do I begin?
Aside from the formal assessment process that is required of departments and core curricular areas, instructors can include assessments of varying designs at any time. Effective instruction includes multiple assessment strategies from simple formative exercises to larger collections of multiple data points.
Will it make me a better instructor?
Absolutely. The more data you have the easier it is to make an informed decision. Assessment is a process not an outcome.