Your source of traffic is the bread and butter for your pay per call success. Choose your traffic source wisely and master it before you bounce to another one by the first sign of failure. The grass is always greener on the other side.
With most of the following traffic sources you can generate purely mobile traffic as well as desktop traffic, tablet traffic or a mix out of those. In the beginning it’s easier to work with mobile traffic only where click-to-call options are available.