The document outlines common mistakes people make when applying for a visa on arrival in Vietnam. Some of the most common mistakes include applying for a visa directly at the airport without obtaining an online approval letter first, assuming a visa on arrival can be used to enter Vietnam by land rather than air, making typos or errors in personal details on the application form, providing an incorrect arrival date that does not match the actual entry date, and believing a visa can easily be extended within Vietnam when the process is actually difficult and costly.