Agency Businesses: How to Stop Poaching Clients / Contractors

I run a tutoring business and I haven't yet really had a chance to witness this because I haven't been contracting tutors for long enough (usually, I still do the majority of the tutoring myself). However, it is obviously a problem for any agency-type business. How I plan to deal with such issues in the future include the following:

• Ensure the contractors are paid fairly
• Provide incentives to the contractors for staying with the company and not taking students on privately (i.e. letting them know you trust their loyalty); not giving them clients or finding clients for them if they poach
• I have a non-compete clause in my work agreement but it is very brief and to-the-point
• Ensure tutors are loyal enough to resist 'temptation' from poaching clients and to always report such activity (added incentives, such as a small bonus or a gift, could be given)

What are some ways in which you or others you know who run an agency business deal with poaching contractors / clients? Do you think it is inevitable? Can you have a company with zero poachers?

I do know that some non-compete clauses can be pretty tricky to push... not every client will want to sign one, and neither will every tutor. If you are taking a large cut of the money from the tutor (or contractor) the client may feel as though they are being duped (and same with the tutor). Some companies go so far as to charge liquidation damages if one should breach the contract. I mean, if you are charging the client $45 / hr and giving the tutor $20, it doesn't seem fair to trap either party in such an agreement.