Reservation Fee or Charge For Referencing or Both?

Hi,

I would like to understand landlords approach to letting a tenant. Woud you either;

1. Charge a reservation fee and deduct from first months rent (no other fees)?
2. Charge for referencing (no other fees)?
3. Charge for referencing and charge a reservation fee if they can't move in straight away and deduct from first months rent(no ther fees)?

What has worked for you?

Thanks

DC