Always tell your translator which target group you are aiming at, so that they can transform your source text into a target text that is customized for that particular audience.
Give your translator enough time to work on your translation. Trust your translator as they know best how many words they can handle within one day without compromising the quality of your requested translation.
You are the expert. Therefore, be available for further queries, and be grateful when your translator comes back to you with certain questions. Do not get this wrong: this does not mean that the translator does not know their craft. The opposite applies here: it clearly shows you that your translator cares, because they want to give you the best translation that is in your interest.
Invest in your translation. When a professional translator commits to your translation project, make sure you pay them accordingly, and you will get a beautiful and functional translation.