How Do We Know if the Good Things We Experience Are the Result of God’s Actions?

Questions about how we know if the good things we experience are the result of God’s actions, whether something can be considered a miracle if it can be explained scientifically, and how to respond to atheists who are mocking a Christian’s prayers for rain.  

• Believers credit God for the good things that happen to them, but good things happen to non-believers also, so how do we know if the good things we experience are the direct result of God’s actions or would have just happened anyway without his involvement?
• Can something still be considered a miracle from God if it can be explained scientifically?
• Recently, a Christian who said he was praying for rain in a drought was mocked by atheists who said prayer won’t create rain. How does one respond to this when the drought continues despite many prayers?