The first and foremost rule is: You cannot force this to happen.
Period. If you try to make it happen, you will fail. If you want, it can be compared to Flying in The Hitchhiker's Guide to the Galaxy, you can only stay aloft if you don’t think about it, otherwise you’ll start thinking this can’t be happening, and then it’s over. What this basicly boils down to is that while you use the techniques you cannot think about doing the action, but rather you must simply act. This makes little sense when first read, I know. You have to simply allow things to happen as you know they are to happen. It requires the proper mindset for this to happen, an outlook where you know what is going to happen and what is happening. It is Zen in practice.

The second rule is this: Everybody has their own method. There is most certainly no set method.
Experimentation is very key and you more likely than not will have to adapt any technique to suit yourself no matter what. The techniques and hints are guides, but following them step by step will not work, you must allow things to happen. Very Zen and Tao

None of my techniques use crystals or incense, never have found it necessary. Just pointing out.

Vibrations are the feeling you will get before you are able to leave. It cannot be described as anything else, but it will be like your whole body will be vibrating but actually none of it is moving. I personally experience a feeling like a second heart beating in the center of my chest that beats very rapidly along with a tingly light feeling all throughout myself.

The Hardest part of Astral Projection/Out of Body Experience(OBE) is the exiting stage. I still do after 3+ years encounter difficultly. Sometimes it just won’t happen, don’t be discouraged, try again later. Because of this and the fact relaxation is easy (breathing techniques, whatever) I will just outline some techs.

Exit Techniques
The Rope Tech:
For this technique you must get yourself comfortable and relaxed whatever way works for you. After the vibrations have started visualize a rope or cord extending from a point in the air or the ceiling. Visualize reaching upwards and clasping this rope with your hands, and then starting pulling yourself out of your body. Continue to do so till you are out.
Spin and Fall:
A more advanced, or at least trickier tech. For this you need to rotate yourself till you are facing downwards (if you are laying on your stomach no need) and simply allowing yourself to fall through the bed/chair/etc. This however can be unnerving if you do not have much experience, as passing through “solid” objects can seem a bit odd.
It Already Is:
For this technique (also a way of moving yourself) you simply know to yourself that things are already that way. You do not try to force yourself out of your body, but rather you are already lifting out of your body, you want it to be like that and it is that way. The language used for this is obviously vague and possibly unhelpful, but the point is to not focus on leaving but the fact that you are already rising.
Gust of Wind:
I have only used this a few times, and I found it accidentally. Essentially you lay on your side and visualize yourself being blown out of your body like a leaf in the wind or whatnot, and in doing so you will suddenly be outside without any time in which you can mess yourself up by thinking.
Lastly on Techniques, remember they are just guidelines and not formulae. Whatever works, works. Do that.

Once you are Out:
Once you are out, you move about by Will. You can travel at any speed you so desire: from walking speed to speed of thought, and can fly, pass through walls, whatever. Simply think yourself forward, or you can try a similar technique of telling yourself it is mighty nice over by the door and simply floating over there because it is so hip and the place to be.
The Astral part of this can be if you choose to travel to other planes of existence. I do this by finding a door, and instead of going through it, simply see it as a gateway to another plane. If and when you choose to do this, don’t try to force yourself to anyone, but just go with wherever you happen to end up. You can pick and choose once you get advanced. Be wary through of falling for the Alice in Wonderland effect as one author (whose name eludes me at the moment) calls it, where you may be traveling around say your house and suddenly are in a room you know isn’t there. In that case you have left the physical plane and more likely are in a dream plane or personal plane of being connected to others. If this happens you can either just explore or return.
To return, simply move part of your physical body. This can and will be difficult. Just remember though if things start getting freaky move your arm or finger and you will instantly be incorporated.

Other Hints:
-Occasionally you will feel a part of your astral body that is stuck; it just does not seem to want to free itself from the physical. I find visualizing energy that soothes the area and causing it to relax will free you.
-It depends on who you ask, but it seems that laying on a north to south axis aids in leaving. I have no reason for this, but I have encountered it in my own experience and I have seen it documented in literature on the subject.
-I have found that you MUST be warm for this to work. This relates to being comfortable, but you cannot lie in your bed and do this if your feet are cold. I am telling you it won’t work.
-No hand positions are necessary, just make yourself comfortable. I have done this curled up in one of those weird positions you get when trying to get comfortable. Being comfortable is the most important.
-More likely than not you will fall asleep on occasion, particularly the first few times. Don’t worry about it, it happens to everyone, plus you get some of the most restful sleep you can this way.

On a final note: Do or do not, there is no try You cannot think about it, simply act.