The most important thing to consider when writing a text is the context in which the text is produced. The content will determine the appropriate style of writing, as well as the type of sources you are expected to use.
When studying at the university you will be expected to write academic texts. Academic texts are typically objective, the content is targeted at an informed audience consisting of other experts, and all arguments and claims made should be supported by evidence either by presenting once own research results or by referring to scientific sources (see Academic writing).
After leaving the university and entering your working life, you will instead be faced with writing texts such as reports, propositions, protocols, official letters, press releases and other types of documents produced by the public sector, organization and private businesses. These texts need to be clear (using plain language) and to the point since they are aimed at non-experts, and you will be expected to a wider array of sources including for example reports from public authorities, laws and regulations (see Writing outside of academia).