Barkoe
Every manager keeps a list, usually in their head, of contractors they would hire again. It is short, and the people on it have less in common than you would expect. Some are expensive. Some are slow. What they share shows up at the end of the engagement rather than the start.
They leave the work in a state you can build on
A good contractor writes down what they did and why, names the two decisions they would revisit, and puts the files where you will look for them. On the Monday after they leave, nobody needs to call. The test is simple: could someone who had never met them continue the work by Wednesday?
Listen to the questions
Before a contractor starts, they ask questions. A weak brief gets weak questions, or none. A contractor worth hiring twice asks who will use the result, what has been tried before, and what you would count as a failure. Those questions take time they could have billed, and they ask them anyway because they want to get it right.
Be someone they want to return to
The relationship runs both ways. The best contractors are in demand, so they choose, and they choose the client who briefs clearly, pays on the day promised and says what worked when the engagement ends. A short note saying this was useful, and why, costs you two minutes. It is worth more to a freelancer than most managers realise, because it is what they show the next client.
Keep the list, and use it
Write the names down. When a project comes up, start with the list before you post a brief to strangers. Tell the people on it that they are on it: a good contractor who knows you would hire them again will keep a week free.