If you've started working with staff or you need to start taking people on, as your business grows - document the processes that are part of your business so you can get an understanding of what needs to be done.
This helps to clarify job responsibilities which can be useful in providing guidance in the early stages, as a new member of staff settles in. It also gives you something to measure their progress and performance against.
This also applies when you outsource work to a third-party. Not only does it help you understand your business better but putting it down in writing may help you to identify gaps in the process that you can tighten up on.
If you're the team leader then you can assess the skills of your team and allocate work appropriately. A mistake many leaders make is to assume that the person they're handing over a task to, knows what's required of them.
Communication is important - you need to be clear about what you want done in order to avoid mis-understandings or wrong assumptions. Tackle the problem upfront. It's important to give timely feedback - both positive and constructive to avoid unwanted behaviour and bad habits developing further.
If you find yourself in the situation where you take on someone who doesn't quite have the skills you expected, you need to make them aware of their skills gap. A clear job description outlining their roles and responsibilities will help, as well as documented processes.