I think the problem with many Christians today is proper discernment. Too often I hear people say God told me this or that and it seems ludicrous to the ear. I would like to know a way people can agree on when talking about these things.
Hearing from God is a very muddy area. Yes we can hear from God, and he can talk to us. But it is my experience that the devil can also speak to us, and often Christians will just follow any voice, and this is not wise.
I look at it this way, God can give a dream, so can the devil, i.e. a nightmare etc. God can give a person a vision, that they can see with their spiritual sight, so to can the devil. In the same way God can speak into our mind or conscience, so to can the devil. The channels of spiritual, visual, and audio spoken to us can be mimicked.
So how do we know if God is speaking? For me I don't know. The bible test us to "test all things" ... to "cling to the good" ... and disregard the bad. Often God will speak using various channels over time, it may start with an impression when reading the bible, He may then use other methods to get His point across. The devil is often impulsive and demanding, but not always.
For me any communication I try to have with God, I do on a low risk level, only things that I know won't hurt me or others. i.e. I pray about what to write in a facebook message, I just let God give me impressions and visions. All low risk stuff.
In the past I was too quick to say "God says" ... and I have made many mistakes. I prefer to be cautious.