From the Miami HEAT's official press release...
MIAMI - The Miami HEAT announced that individual game tickets for Game 6 of the 2013 NBA Finals between the Heat and the San Antonio Spurs will go on sale to the general public June 14 at 2:00 p.m. Individual game ticket inventory is limited and tickets are expected to sell quickly. Fans can purchase tickets online at HEAT.com, Ticketmaster.com or by calling 1-800-4NBA-TIX. There will be an eight ticket purchase limit per household.
Tickets will NOT be available at the AmericanAirlines Arena Ticket Office for the initial on-sale date. Playoff tickets may be purchased at the AmericanAirlines Arena Ticket Office beginning on Monday, June 17 at 10:00 a.m.
In addition, American Express cardholders can purchase American Express® Dewar's Rail seating, including valet parking and a premium buffet dinner for Game 6 starting at 10:00 a.m. tomorrow. Dewar's Rail seating can be purchased online at HEAT.com or Ticketmaster.com. Tickets are $1,500 each and subject to availability. Any remaining Dewar's Rail seating will be available to the general public starting tomorrow at 2:00 p.m.
HEAT fans interested in lower level seats are encouraged to register for HEAT Game Time Tickets. HEAT Game Time Tickets are VIP seats in the lower level normally reserved for NBA executives that may be released for sale approximately 48 hours before game time. If and when HEAT Game Time Tickets are released for sale, HEAT fans that register their contact and credit card information on HEATGameTimeTickets.com will be contacted by a HEAT sales representative to complete the ticket purchase.
Game 6 will be played at AmericanAirlines Arena on Tuesday, June 18 at 9:00 p.m.