Hello there, to all of those who have trouble with the astral projection (or the Vision of the Spirit, as it's also called..in a more poetic fashion).
I remember I used to have a lot of trouble with this particular subject, but most of all, because I had no idea what astral peojection really was. Once I tried a few techniques, I finally found one that was suitable for me, but that was after years of trying! (this is also an important tip, try using several methods of astral projection until you find which one is the best for you.)
Now, and probably the most important thing (or at least, it was for me), at first, astral projection will feel like a fantasy or daydreaming. You'll feel like you failed because it was just a fantasy. And this is where most people fail. Yes, it feels that way, at first. If you keep the practise up, you'll notice that these "fantasies" will be more vivid, and less things will be out of your conscious control.
Now, a way to check if,after you finished, you really projected, is to pay atention to what happens in your life afterwards. I remember doing some astral working with the planet Saturn, and the next day, I accidentally got a cut on my right foot. Now, feet are commonly associated (in the Qabalah) with the path of Saturn in the tree of life. It took me a while (and a friend to point this "coincidence" out) but when it did hit me, I realized I had succeded.
Now, I'll give you my favourite technique of the "Vision of the Spirit" (I really like this name, call me a sucker for poetics). I teach this one to every one of my students, and they've all succeded at their first try (even if some of them thought they didn't and that it was just their imagination running wild! this is the key to astral projection, letting your wildest parts come)
Take a bath, or a shower, whichever you like to be clean. Was the top of your head with cold water (this'll help a lot).
Choose a comfortable position (a semi-lotus asana works best, I don't encourage lying down because you might fall asleep or get distracted by itches and stuff) and relax. A good relaxation technique is to visualize a cloud of golden light enveloping one by one every part of your body and relaxing it.
Now, you are really relaxed and your mind is quiet (I could also suggest at this point, casting a Circle, or using some other ritual variation of the Lesser Banishing Ritual of the Pentagram) Call upon the Gods (or the Divinity, or Higher Self, whatever you want, or just vibrate Divine o Holy Names), and close your eyes.
Now picture yourself standing up in a room (try, at first, to keep this room as bare and simple as possible, with practise you'll be able to decorate it and turn it into an astral temple). An important (EXTREMELY) tip, is to visualize it from inner perspective, I mean, using your visualized body's eyes instead of visualizing yourself for the exterior.
Now, feel yourself walking, it will feel fake at first, but ignore this sensation, until you find, between two pillars a veil. This veil is see through, and, on the other side of the veil, there is a copy of your body. Stand in front of the veil. NOW HERE IS THE MOST IMPORTANT MOMENT, transfer your view point to the other body. Give it a second for the sensations to accomodate. Use this new body to keep walking through a corridor, leaving, for now, your other body behind.
Now, I'll be assuming you have some knowledge of symbols, so I won't explain this in detail. But before you start, you should have chosen a symbol. This symbol will be used as a door to a certain part of the astral plane. This is useful for several reasons: it'll help you investigate in depth an energy, and it will keep you from wondering without destination through the planes. There are infinite symbols you can choose. I recomend, for beginners, either elemental alchemical symbols or hindu tattvas (which are basically the same). Once you get used to this, you can move to other symbols: planetary symbols, zodiac symbols, runes, ogham, hebrew letter, sigils, tarot cards (oh, yes, they can be used this way, and it will give you more knowledge of tarot and elemental/planetary/zodiacal forces than you'll ever find in a book) and whatnot.
Picture yourself standing in front of the symbol, it could be a door, it could be another veil, it could be a curtain, you don't know it until you see it. Now go through the symbol and enjoy.
Once you finish whatever you do there, go back through the same path you went. I CAN'T STRESS THIS ENOUGH. Go back and exit through the symbol, go back the corridor and to the veil. Return your point of view to the body behind the first veil. Go back to the place you started this whole journey and open your eyes.
After you finish this journey, make a ritual cleanse, either with aspersions and incense or a variation of the Lesser Banishing Ritual of the Pentagram. This is mandatory!!!!!!
It's important to write down every single thing you see or "imagine", every single conversation with the beings from the other planes, and every single detail. In time, it will become extremely useful.
It can happen (it happened to me) that sometimes, something from the outside (phone ringing, dog barking, someone barging into your room, etc) makes you open your eyes in the middle of the journey. When this happens, it'll feel really weird, like a mind buzzing. I have a few theories of why this happens, but once it does, take a shower, eat, work out, take a walk, play with your pets, watch TV...it'll fade, but it's still an uncomfortable thing. Even if you are interrupted, banish anyway, and don't try it again for at least 24 hours.
Well, I hope you try this, and I hope you write your experiences.
I wish this will be useful