Many aspects of employee conduct and performance are covered by workplace policies and procedures such as the Code of Conduct, Performance and Misconduct Policy, Attendance and Absenteeism Policy etc.
Prepare policies that cover the various issues in your business, back them up with procedures (which are steps for implementing the policies in a practical way) and make sure they are widely publicised, explained to employees, and that employees clearly understand them.
Very small businesses may regard putting a bunch of policies together as onerous and unnecessary. However, court cases have held that even the smallest businesses should have policies in place. If you are not sure which policies are appropriate for your business, you should seek advice.