Biblically, what do we know about good and evil? Well, there are a couple of salient points. We know that the comparison is sometimes in terms of light and darkness (e.g., John 3:19-20; 1 John 1:5-7). We know that our good works produce glory for God (Matt 5:16). Perhaps there's a hint in there to see how we can bear good fruit.
Paul told the Philippians that they must work out their salvation and told them how it was done. "It is God who works in you, both to will and to work for His good pleasure." (Phil 2:13) There's a really good clue. In this scenario the "work out your salvation" that we accomplish is motivated ("will") and powered ("work") by God. Is it possible, then, that God's definition of "good" is "that which is done by God for God"? I think so.
In our favorite "saved by grace through faith" passage (Eph 2:8-9), we find this: "For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them." (Eph 2:10) So, with Jesus's "good trees bear good fruit" imagery, this "good fruit" is prepared by God beforehand; we just walk in them. Jesus said, "Whoever does what is true comes to the light, so that it may be clearly seen that his works have been carried out in God." (John 3:21) There it is again. Our good works are a product of God's work in us. And, if you look back at the earlier reference, you'll find it's there, too.
This is the message we have heard from Him and proclaim to you, that God is light, and in Him is no darkness at all. If we say we have fellowship with Him while we walk in darkness, we lie and do not practice the truth. But if we walk in the light, as He is in the light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin. (1 John 1:5-7)God is light. So when we "walk in the light" we do what He enables and provides.
It makes sense, then. We do not produce good works ("There is none who does good."). God does. "Good" is defined as what God does. The good works that we do are produced by God for God's glory. That's the "good fruit". And, see? We all know that fruit doesn't produce itself. We, then, will either produce the fruit of our sin natures or we will allow God to produce the fruit of His glory. The amazing part of this is that He then rewards us for His working out good in us. Now that is astounding.