Hire two people for each job

Sometimes this isn't possible for cost reasons, but there are a few benefits to this:

1. If they both can cover 90% of a task/problem, etc, the combined coverage is 99%.
2. They inspire/push/learn from each other
3. You will always have someone to cover a role if/when one of them leaves or underperforms.
4. They will keep each other honest

This is much like markets. One supplier leaves customers (in this case you as the employer) without any leverage. With only one provider, there is a mini monopoly which limits your ability to navigate complicated situations.