Find a festival. There are dozens of hot air balloon festivals in the United States and other countries. Some are large national championship competitions, but most are small regional events. Some of the more well known festivals are the Albuquerque (New Mexico) International Balloon Fiesta, the National Balloon Classic (Iowa), Baton Rouge Hot Air Balloon Festival (Louisiana), and the New Jersey Festival of Ballooning.
Check the festival's website for a schedule of daily events. Festivals have to follow tight schedules for launches and landings. Balloon flights are usually scheduled early in the morning or a few hours before sunset to take advantage of calm winds.
Check the weather report or the festival website if there is threatening weather in the area. Weather issues are the main reason a festival could be canceled or delayed.
Check the festival for any balloon ride opportunities. Some festivals offer trips for the curious, though there is usually a price involved. There may also be tethered flight for those not quite ready to leave the earth completely.
Stay for the "night glow" event. A night glow is when the pilots inflate the balloons but keep them tethered to the ground right after sunset. When the burners are turned on, the balloons glow in the darkness.