Remember you are working with an energy greater than yourself. You must be at one with the element before it can affect you. Feel that you are made of only the element you have chosen. Say to yourself, "I am one with Infinite (name of element)," until you feel as though you are that element. Feel the infinite energy of the element coursing through you, and know that it has the power to affect you. See yourself as taking on the characteristics that this larger power possesses.
A useful exercise is practicing becoming in tune with the different elements.
For water, float in a pool or play in the bath;
for earth, go lie down in a field or forest, or even in your own backyard;
for air you can visit a windy hill or sit in front of a fan;
for fire, sit in a desert or a dry sauna. If this is unavailable, you could turn up the heat in your home.
Breathe in the element feeling its energy fill you, cleansing you, then breathe out letting the element take out any impurities with it. Spend at least a week on each element. Then practice becoming the element. With steady practice you will get results.
Now you can guide how this greater energy will specifically affect you. A good way to do this is to think about the area you are trying to heal (if you are interested in healing yourself, for example), and give yourself affirmations such as: My stomach is peaceful and tranquil. Or: The pain is gone. Or you can even just use one word affirmations like: Peace, tranquility, soothing, etc. You are in effect taking the broad characteristics of an element and trying to narrow it down to your specific problem.
Keep up your concentration until you have an effect, which is not always easy to do, especially if you are experiencing great pain. Feeling one with the element, focusing it on a particular problem, while saying your affirmations, all at the same time. It can get a bit difficult, but the rewards are worth the trouble. It may take several minutes to achieve results, depending upon the problem.
If after many minutes of concentration you have not received the full benefit, try letting go of the images and let the element follow through on its own. This is especially true in cases of diarrhea, which usually takes several hours. You may have to use several treatments until you achieve the desired effect.
After you know what each element can do, you can tailor your treatments to a specific purpose.