One of the essential first steps of a tenancy is to sign a tenancy agreement with your tenants to make it clear what is expected of them to have a successful outcome for both of you. Most landlords don't put in enough clauses in their tenancy agreement to spell out what is required of the tenants (the DBH standard contract assumes everyone has a working knowledge of the Residential Tenancies Act, but I bet most landlords have never read it, let alone their tenants). Also, many put in clauses that will not be enforceable should the tenancy end up in Tribunal (a classic is 'tenants will commercially clean carpet upon vacating'. This can't be enforced as it isn't 'reasonable' to expect that, so is pointless to have it unless you add the magic words 'if required').
Our tenancy agreements have 34 standard clauses, plus we add more in for special circumstances, such as the tenant having a pet (that takes 3 extra clauses!), if they need a guarantor, or can't pay all the bond or rent on the day they sign the contract. We also discuss all of these clauses with the tenants, we don't just thrust the contract at them and say 'sign here'. As a result of our process we have great success in tenants taking care of the property and leaving it in good order.
If your tenants can't seem to look after the property, it could be your contract is lacking the right clauses to make your (legally compliant) expectations clear. We can help you.