The spiritual energy used for astral travel is associated with the 6th chakra. This is the energy vibration/frequency that is most conducive for astral travel. As a result, you should engage and use the tools which help create, nourish, clear, and vitalize the 6th chakra energies.
A desire is not only needed for astral travel, but also clarifies what specifically you are desiring to accomplish by traveling to the astral plane. Do you want to meet and converse with your Higher Self? Do you want to meet and converse with your Spiritual Guides? Who and what is it that you want to do once you get to the astral plane? This process of clarifying your desire will help provide an "address" so once you get to the astral plane, you will arrive at the specific place you desire. (Also, by visiting your Spiritual Guide, for example, you will have someone who can serve as an escort and guide so you won't get lost).
If (and when) you travel to the astral plane, you won't readily recall the experience because of the "veil" which essentially prevents the ability to carry over the memory of this travel experience. That is why it is necessary to first train to remember and recall the experience. Even with training, some of the first memories you bring back will be sensations, such as the feeling of slipperiness, or "popping out of water". With more memory training you will eventually be able to bring back more of the experience, but recall process may be in dreams or impressions, and not always immediately after the travel. (See "Remembering Your Astral Travel" to learn how to train yourself to recall astral travel).
Practice is about focusing and directing your mental thoughts and desires on having your soul expand outside of your body. This type of practice and training can happen during during meditation, or after you have sex, or before you go to sleep. You mentally focus on expanding out side the body and lifting. This repeating mental focus engages your mind and trains your soul to expand.
You can train yourself to travel to the astral plane. By using the tools for the 6th chakra, clarifying your desire to travel, training yourself to remember the travel experience, and then practicing, you may be able to experience the joys of astral travel.