THROUGH HIS CREATION.
Psalms 19:1 For the director of music. A psalm of David. The heavens declare the glory of God; the skies proclaim the work of his hands.
Romans 1:20 For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that men are without excuse.
THROUGH THE WORD.
2ND Timothy 3:16-17 All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work.
THROUGH HIS PROPHETS.
Numbers 12:6 he said, "Listen to my words: "When a prophet of the LORD is among you, I reveal myself to him in visions, I speak to him in dreams.”
Genesis 46:2 And God spoke to Israel in a vision at night and said, "Jacob! Jacob!" "Here I am," he replied.
Genesis 15:1 After this, the word of the LORD came to Abram in a vision: "Do not be afraid, Abram. I am your shield, your very great reward."
Numbers 12:6 he said, "Listen to my words: "When a prophet of the LORD is among you, I reveal myself to him in visions, I speak to him in dreams.
1 Kings 3:5 At Gibeon the LORD appeared to Solomon during the night in a dream, and God said, "Ask for whatever you want me to give you."
FACE TO FACE.
Numbers 12:8 With him I speak face to face, clearly and not in riddles; he sees the form of the LORD. Why then were you not afraid to speak against my servant Moses?"
Hebrews 1:1-2 ¶ In the past God spoke to our forefathers through the prophets at many times and in various ways, but in these last days he has spoken to us by his Son, whom he appointed heir of all things, and through whom he made the universe.
John 14:24 He who does not love me will not obey my teaching. These words you hear are not my own; they belong to the Father who sent me.
Judges 2:4-5 When the angel of the LORD had spoken these things to all the Israelites, the people wept aloud, and they called that place Bokim. There they offered sacrifices to the LORD.
Matthew 2:13 When they had gone, an angel of the Lord appeared to Joseph in a dream. "Get up," he said, "take the child and his mother and escape to Egypt. Stay there until I tell you, for Herod is going to search for the child to kill him."
Revelation 22:6 The angel said to me, "These words are trustworthy and true. The Lord, the God of the spirits of the prophets, sent his angel to show his servants the things that must soon take place."
THOUGH HIS PRESENCE.
Exodus 33:19 And the LORD said, "I will cause all my goodness to pass in front of you, and I will proclaim my name, the LORD, in your presence. I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion.”
BY VOICE ONLY.
Deuteronomy 4:12 Then the LORD spoke to you out of the fire. You heard the sound of words but saw no form; there was only a voice.
Matthew 3:17 And a voice from heaven said, "This is my Son, whom I love; with him I am well pleased."
Acts 10:13 Then a voice told him, "Get up, Peter. Kill and eat."
Acts 9:4 He fell to the ground and heard a voice say to him, "Saul, Saul, why do you persecute me?"
BY WAY OF A FLEECE.
Judges 6:36-40 Gideon said to God, "If you will save Israel by my hand as you have promised—look, I will place a wool fleece on the threshing-floor. If there is dew only on the fleece and all the ground is dry, then I will know that you will save Israel by my hand, as you said." And that is what happened. Gideon rose early the next day; he squeezed the fleece and wrung out the dew—a bowlful of water. Then Gideon said to God, "Do not be angry with me. Let me make just one more request. Allow me one more test with the fleece. This time make the fleece dry and the ground covered with dew." That night God did so. Only the fleece was dry; all the ground was covered with dew.
Numbers 22:28 Then the LORD opened the donkey's mouth, and it said to Balaam, "What have I done to you to make you beat me these three times?
I’m certain my list can be added to, but I think this is a reasonable start. Though you never want to limit the LORD, you always want to ‘test’ everything. What are the parameters of ‘testing’? The Word. The Bible. The Truth. If it’s not matching up with those teachings, I’d be very, very careful. Always remember that there’s an enemy out there, and he’d love to ruin you. We can also be enticed by our own desires and presumptuousness.