My sister and I actually used a Ouija board to find ours. We were pretty paranoid about protections and stuff to make sure good things came through. If you'd rather not go through that route, meditation would be safer and probably more interesting! You could also try Scrying. A bowl filled with black water would be good for that. Takes some practice to get used to, though. Then again, so does meditation. :)
Keep trying! Sooner or later someone will come through. Sometimes you end up finding out that you have multiple guardians. I have a minimum of five, apparently.
You may have one. I believe that it is likely. In my view, a guide is a spiritual being who, to our senses, would seem as a floating ball of consciousess. Just as you yourself are simply consciousness within a physical body.
You must be receptive to spirits to communicate with a guide. Physical life usually makes you so physically attuned that you forget or ignore your spiritual side. Work on strengthening your spiritual awareness, awareness of your thoughts, consciousness, etc... and you can get closer to being able to sense or possibly communicate with your guide. Most communications they give you will be in the form of thought waves. It is possible for you to sometimes also see these things in your dreams. But it is tricky knowing which dreams aren't just fabrications of your mind. =p