Jesus made it fairly simple, at least to start. He said, “Follow me.” The word follow, diluted by our culture, begs for a biblical definition. In English, you can follow the directions (or not); you can follow a sports team (by simply reading the paper or watching TV); you can “follow your bliss” (though that might not get you beyond yourself); you can follow someone on Twitter (even if you don’t actually know them).
When Jesus invited a group of first-century Jewish fishermen and political Zealots to follow him, he didn’t mean “Let’s just keep in touch.” He literally meant, “Come with me, right now. Live as I live. Learn a way of life and faith from me by watching.” And some people did, but others did not. It was hardly surprising that young men working in their father’s fishing business walked away from that. The most highly revered career in that time was to be a rabbi. To “give up” a blue-collar job to become the follower of a rabbi (and therefore go into training as a potential future rabbi) was a no-brainer.