Clairvoyance is the apparent ability to gather information about something through extrasensory perception. “Extrasensory perception or ESP, also called sixth sense, includes reception of information not gained through the recognized physical senses but sensed with the mind.” http://wikipedia.com
Clairvoyance is considered clear, as in you clearly see the future or past. There are ways to be able to become clairvoyant by using your natural senses to discover your sixth sense (your clairvoyance)
For starters you will have to let go of any fear that you have, whether it is fear of seeing the future, or fear of seeing the past, you need to clear your mind of the fear. You will need to ask straight forward questions in order to get a response, you cannot make a round about statement or question and expect an answer. You have to be focused on your third eye, this is your extrasensory esp, pay attention to anything that comes across your mind, pictures especially. Imagine this picture that is coming to you, and enlarge it in your mind to get a clearer vision of what this is, believe in what you see, and take it from there.
These steps will help you become clairvoyant, if you want to be able to do this practice, focus intently, and pay attention to everything that comes across your mind.