I believe that there are a few kinds of visions. Some are spectacular and come in our dreams and when we are conscious. Some of our visions are not so spectacular.
Many times when we refer to visions, we refer to the spectacular ones, where God reveals to us in a vision to do something. It is so clear and vivid in our minds. God may choose to use this method but many times God uses simple ways to talk to us.
Many times, God speaks to us through mental pictures, through impressions or through visions. We see something in our mind.
Just like when we hear from God, we do not have to hear an audible voice from God to hear from God. God can speak to us through the bible, through a small still voice, through our inner witness or through visions.
We do not limit God. But if we are to receive anything by God, we need one element: faith.
6 But let him ask in faith, nothing wavering. For he that wavereth is like a wave of the sea driven with the wind and tossed.
7 For let not that man think that he shall receive any thing of the Lord.
Many times to get anything from God, the simplest way is to ask in faith and expectation.