Use language that is appropriate for the setting, but still clear and concise. The more direct the language, the more effective it is. If, however, your employer insists on using the traditional legalese, then tread carefully. Write in the active voice. An active sentence is one in which the subject of the sentence is engaging the object of the sentence.
Active writing is more direct and stronger than passive writing.
Active writing can also promote clarity. When the actor of a sentence is unimportant for sentence purposes, passive writing is preferred. But if you really want to improve the level of your writing skills, legal or otherwise, reading more will help accomplish that desire. The more we read, the more we are exposed to others' ideas, sentence structure, and choice of words. I guarantee that your writing will improve as you read that which challenges your reading skills.