Venus never climbs very high in the night sky. It will always be seen fairly close to the horizon and only early in the evening or morning. This is because venus is closer to the sun than us. Because of this it is never on the opposite side of the earth as the sun.
Venus looks like a very bright star near the horizon. When you look at it in a telescope it will always appear as a crescent. For something to appear full, it has to be on the opposite side of the earth as the sun.