Policies
As well as setting out sick pay in your employment contract, in order to comply with employment law you should have a handbook in which you set out the policies to apply in relation to sickness absence. . A paper trail and evidence of good communication with your employees is important in any employment law claim.
There are two particular areas of employment policy you can think of reviewing - reporting sickness absence and back to work interviews/appraisals. If the employee reporting in sick is being disingenuous they are likely to ask a partner or friend to report in, or may prefer to leave a message. This can be resolved by tightening up the reporting procedure: give the name of the person to whom they must report and the time they should call. Make it clear that you expect the employee to call and not someone on their behalf, as you may need to check with the employee about covering their work for that day. Set out how you will police this policy and the sanctions if they fail to follow it.
Most employers mean to have back to work interviews, but tend to ignore them unless there is a problem with a particular member of staff. This is not ideal as the Courts and tribunal expect you to treat all staff in a consistent manner rather than applying one rule for one and a different rule for another. If you, or your line managers generally, tend to ignore the requirements to have back to work interviews with staff then you could have yearly or half yearly appraisals that review attendance, with a follow up if a problem appears.