Depends how big it is.
The best option is to cut the tree down, then treat the stump with suitable chemicals to prevent regrowth. Small trees could be done by yourself with extreme care (using tools and avoiding falling branches) but a well established/mature is best left to the specialist tree surgeons.
I had two 10yr old sycamores in my garden that I cut down, a tree surgeon then came and ground the stumps down below the soil level with a special tool. They have not re-grown. It did'nt cost much and I did'nt need to use herbicides.
With no disrespect to Hammer, the copper nail thing is just an old wives tale. It doesn't work. Never try to kill a tree slowly. It can weaken and fall in a storm on whatever is nearby. That could be a person or a building.
As others have suggested, best to have it cut down and the stump ground.