Well written policies and procedures which are communicated and applied consistently are the key to ensuring that the risk of discrimination is reduced as much as possible.
Employees (as well as workers and job applicants) could bring claims for discrimination on the basis of Age, Gender, Race, Beliefs, Marital Status, Disability and Sexual Orientation.
Care must be taken not to over generalise i.e. “everyone must wear trousers” or “everyone must work on a specific day of the week” as this could have a disproportionate negative impact on a sub sect of your workforce. Therefore you end up discriminating against some, as a result of trying to treat everyone the same.