Dear Puja,
Fundamentals will remain the same whether you are working in a big company or a small one. Please check Google and citehr for the required information. You should choose an appraisal method as per your organization's requirements. Mostly, small companies (less than 30 employees) have a traditional appraisal process in which the appraisal is done by the boss. You should try a new approach (MBO, PMS, 360 Degree) so that it helps the organization in the long run.