“I am wondering how you can tell the difference between the inner voice of God and of Satan. I know sometimes it’s obvious, but other times I wonder if it’s Satan speaking to me or God. I would appreciate insight on this.”
You speak here of two voices: that of God and of Satan. You could actually speak of three voices: that of God, of Satan, and the voice of our own fleshly desires. Satan certainly does speak by way of our inner voice. He did so to Jesus (Mat. 4:1-10), but was strongly rebuked by Jesus. Satan did so to man as well (Acts 5:3), but man fell for it, and brought man to a tragic end. When you hear Satan whispering in you – you will often find that it harmonizes with the voice of your own fleshly desires. Satan’s goal is to see you cater to the flesh, doubt God’s Word “Has God said?” (Gen. 3:1), get you trapped in sin, leave you anxious and troubled, and, if he gets his way, push you towards a tragic end.
Satan is a deceiver and is devious, in that he will sometimes use the inner voice to contradict God’s Word “You will not surely die!” (Gen. 3:4).
On the other hand, when God speaks by the inner voice, He always speaks according to His revealed Word. He may convict you of a sin, and create discord with the inner voice of your fleshly desires, but will never leave you without hope. When God speaks, His goal is to direct you to the saving work of His son Jesus Christ, to lift you up by His Holy Spirit, to encourage you to do what is right, honest, and praiseworthy, and lead you to peace with Him.