There are two known ways of getting into this altered state, which some describe as the "Zone".
1) self-hypnosis - affecting the subconscious
2) Alpha state (where alpha brainwaves are dominant), it is called crystal countdown (from Laurie Cabot's book) in which you meditate to get into the "alpha state".
I do not think these two a mutually exclusive, but many people swear by number 2. What do you use? What is your preference?
Let's look at the brain waves...
Beta – 14-20Hz Normal waking consciousness
Alpha – 8 -13Hz Daydream, meditation, creativity
Theta – 4-7Hz Heightened creativity, Psychic work, deep meditation
Delta - .5 – 3Hz Deep sleep, unconsciousness
*White noise is useful in overwhelming the conscious mind
*Both Alpha & Theta waves are needed for Trance States = peak performance.
There is a way I get into my alpha state (I am still working on theta...)
The Alpha Countdown
Close your eyes and clear your mental screen.
Then create the following numbers one by one in its respective color on your screen (mind's eye).
7 - red
6 - orange
5 - yellow
4 - green
3 - blue
2 - indigo
1 - purple/orchid.
Keep the numbers on the screen for as long as you like, but keep focused on the number and how you sink deeper and deeper for every step/number.
Once you have reached alpha, I suggest you do some kind of cleansing before you continue your meditation, such as saying "I am now in alpha and I am giving myself a complete cleansing", or washing yourself with white light, or pulling all negativity out of your body and throwing it into a well/toilet/river beneath a bridge.
If you want to put a more advanced touch to this, you can make these numbers appear on the steps of a spiral staircase going down. Then each step will really take you deeper down into alpha! When I do this, for every step I take on my murky stone staricase I say "deepest psychic and creative level". When you get to the bottom you reach your meditational kingdom and only you can tell what you'll find there...
After many weeks of practice you can build a mental trigger like crossing your fingers, while deep in the Alpha state and equate that action to instant Alpha. After that you can get into Alpha very fast. It is a mater of practice and acquired belief. If you do not believe in this it won't work for you no matter how many proofs and tests one would present to you.
"When you have reached a point at which you cannot see more, You must remember that there may be a point beyond this at which you can see everything." -Mehmet Karagoz