My preferred method is to grasp the spur near the base with some pliers. Gently twist back and forth until the outer spur loosens, then lift off with your fingers. It will be like a hollow "horn". What remains is a soft nub, and there could be a drop of blood on it. Clean it off and put some ointment on it. It'll harden is a day or two.
The spurs will take over a year to grow back.
You can use dog/cat toenail clippers to cut off the major portion of the spur, but this risks cutting into that inner nub and you could have some heavy bleeding.
Also, there's the hot potato method. Heat potatoes, and place on the spur for a few minutes until the spur loosens, then lift the spur off. There's usually no bleeding with this method, but you risk burning the rooster if he gets wiggly on you.