In YOUR opinion, what is needed for a well-trained dog?

Some people believe you need treats and some believe you need an E-collar, prong collar and discipline. Of course there's always time and patience. In your opinion what is needed for a well-trained dog? Why? Do you believe that everyone NEEDS to go to a trainer? What would you say is the best method? Also, what exactly is the point of a clicker? Couldn't you just give praise and have that be the same thing as a clicker?