how is each believer to serve God in His vineyard?

Every Grace Age believer serves as an ambassador for Christ, letting the world know they have already been reconciled. God did not save believers just to sit or escape hellfire; they are saved to serve and be useful in His vineyard in whatever particular capacity He gives each one.

Les explains that the believer's service flows from being a new creation in Christ and an ambassador for Christ. Every Grace Age believer has the responsibility to let the world know that they have already been reconciled—it is done and finished. Just as an ambassador in a foreign country does not isolate himself but stays in communication with his home government because he is an employee of that government, the believer is to be useful in God's vineyard in whatever particular capacity God may give to each one. Les emphasizes that God did not save us to sit or merely to escape hellfire, but saved us to serve. He also connects this to Isaiah's words: now is the accepted time; now is the day of salvation.

2 Corinthians 6:1

We then, as workers together with him, beseech you also that ye receive not the grace of God in vain.

How are believers supposed to serve in God's vineyard?

Believers serve as ambassadors for Christ, letting the world know they have already been reconciled to God. They are saved to serve, not to sit or merely escape hellfire, and are to be useful in God's vineyard in whatever capacity He assigns to each one.