For lack of a better phrase, diligence is key. Understanding the market and the distributor/staff you hire for the sub. Being clear about targets, process, etc. The biggest mistake I see--well, one of the biggest mistakes--is that businesses don't invest time in review/oversight. Some think that once the contract is signed, their effort is done. In a distribution agreement, for example, you insist on periodic reporting (against targets/benchmarks), information sharing/reporting on clients' information and audit rights for both--and exercise those audit rights periodically, and not just when you suspect something is wrong. A well drafted agreement at the front end will not just set expectations but can save a later headache.