What does the astral plane look like? Is it the physical world from a spiritual point of view? If so, couldn't this be a form of spying, as you could just follow a person around? Also, what happens when you get to a place where you haven't explored physically and you don't know what it looks like? What do you see? This is assuming the first and second questions are true...
Are there dangers to astral projecting? Like bad spirits etc.
Finally, how would you suggest one proceed to astral project?
Well I only projected once, so my knowledge on it is very limited. But from what I am told and from what I have seen, when you astral project, you leave your body. You can then explore the world as you wish, If you never seen it before, it will look the same if you did see it, all your doing is viewing it when your outside your body.
Like I said, my knowledge is very limited so I can't answer your other questions.
It is not the physical world as we know it but it can look very similar since that's what our mind knows. It is also in a higher dimension and so sometimes things can manifest themselves there first and may later happen in rea. This is why sometimes people get dreams (which occur in astral) and later on those dreams "come true". (Note, not all dreams are astral experiences...sometimes it can just be your subconscious replaying things).
Everyone's astral experience can be very different. Sometimes you find similarities in other people's experience and sometimes you don't. Even the way you get into astral varies from person to person.
You can meet harmful spirits yes, but they cannot take over your body. You can protect yourself by shielding/protection circle.
There are many ways to astral project. You can try relaxing your body almost to the state of falling asleep and then willing yourself to get up out of your body, one limb at a time (a tingling sensation or vibrations are an indication that you are getting there). Most people use this or a variation of this method.
Another method is through dreams. If you become aware that you are dreaming, it's as easy as activating one's mind here (since you are already in astral..ok maybe not so easy because you'd first have to acknowledge you are dreaming and "wake" up your mind) and so your active mind can then control where you go in astral. I've done this form many times.
Oh to answer your question of what happens if you end up in a place you've never been before in astral. I can only tell you of my own experience here. Once I stayed over at a friend's home and had never been to the second story of the house (my friend lived on the ground floor). During the night I astral projected (note, I have been astral projecting spontaneously since I was a kid). I exited my body with such a force that I ended up going through the ceiling ended up second floor, and I stopped short of a framed photograph of a baby girl and I remember a dining room table with white lace table cloth. The next day, I asked my friend and he was able to confirm that yes, my description of the photograph and the table cloth were spot on, but how on earth could I have possibly known that, he asked.