In deciding on a level of formality for your writing, consider both your subject and your audience. Does the subject demand a dignified, serious treatment, or is a relaxed tone more suitable? Will the audience be put off if you assume too close a relationship with them, or might you alienate them by seeming too distant?
For most college and professional writing, some degree of formality is appropriate. In a letter applying for a job, for example, it is a mistake to sound too breezy and informal.
Informal writing is appropriate for private letters, business correspondence between close associates, articles in popular magazines, and personal narratives. In such writing, formal language can seem out of place.
Formal words such as commenced and implemented clash with appropriate informal terms such as sucker pitch and fast windup.
Exercises:
Jargon, pretentious language, euphemisms, and doublespeak 1
Jargon, pretentious language, euphemisms, and doublespeak 2