C-1 Visas or Transit Visas Requirements: 

Passing in immediate and continuous transit through U.S. 

Immediate is defined as reasonably expeditious departure in normal course of travel as elements permit and prearranged itinerary assumes. No unreasonable layover privileges. If you want to visit friends then you need other type of visa. 

If C-1 is for a crewmen joining a ship, they needs a letter from shipping company agreeing to pay cost of deportation if necessary.

• In possession of ticket or other assurance of transportation to destination.
• Sufficient funds for transit.
• Has permission to enter a third country.
• Period of stay cannot exceed 29 days.

Other issues:

• Cannot change status.
• Can adjust under certain circumstances.
• Cannot adjust if C-1 crewman.
• Ineligible for extensions of stay.