Place TNT on the ground
Ignite it with flint and steel
Ignite it with a fire charge
Power it with redstone
Use a lever, button, or pressure plate connected to redstone
Use a redstone torch or redstone block
Shoot it with a flaming arrow
Hit it with a dispenser-fired fire charge
Cause nearby TNT to detonate
Use lava or fire to ignite it
Use an explosion to trigger it