Study the theoretical reasons for developing a language. One of the most common theoretical reasons is to improve your sense of worldliness by improving your ability to connect with other cultures. Additionally, you are more marketable with the ability to work in foreign economies. For children in particular, developing language is important for basic cognitive development.
Improve your own native language skills and study a foreign language in order to internalize the rationale for language development. By developing language skills independently, you will better familiarize yourself with the challenges and benefits of developing a language. Consequently, when you finally write a rationale for studying a foreign language, you are likely to create more fluid, honest sentences that appeal to readers on a deep and intuitive level. Review whether your own perception of the challenges and benefits of learning language are consistent with the literature on the subject you read. Reflect on the similarities and differences before writing.
Write a draft version of the article and ask others who pursue language development to critique it. Ensure that the rationality and technical writing level of the article is appropriate for the intended audience. For example, if writing a piece for children in grade school, you will obviously need to appeal to different interests and values and be less technical than when writing for a college student.
Request feedback on the article from the audience it is designed to persuade. For example, if teaching a foreign language class in college, present the article in class and request a short paper from each student and a class-wide conversation on the paper the next day. Edit the article over time as necessary.