You need a passport that is still valid, bank statements from the last six months, and at least two photos that are still good. These should all be looked at. The documents should only be able to be scanned by the system that handles visas. If any of the documents are left out, the user should have them checked. After the documents have been checked, a special stamp is put on each one to show that the scanning process is done.
If you are going with someone else, you should also have a ticket to get back home. The dates on your return tickets should match the dates on your visas. If they come back after your visa is over, you won't be able to apply. Then, to change your visa, you have to pay extra fees that depend on where you live and what kind of visa you have.
People with any kind of health problem should have a note from their doctor saying they can travel between their medications. It is very important to follow all rules about who can travel, especially if you are sick or have been told not to travel. They should get a note from their doctor if they need to travel this way because of an emergency.