Earth
Surprisingly, this is energy that comes from the Earth. The Earth is often associated with strength and so its energy can used to stabilise things and support them. It has also been known to be associated with slowness, so for a bit of timing you could add this to your works.
There are a couple of methods I know of for accessing Earth energy, one is best when you plan for directing the energy into something else, be it to hold it or to weave it in with other energies, whilst the other method is best for using on a larger scale, with your whole body, or just testing how much you can feel the energy.

The energy of the earth may appear as a placid green, for me it is the colour of foliage in a shadowy forest, a dark yet calming and peaceful green.

Method one:
Sit in a comfortable position, clear your mind, and put your arms out beside you (or, if it is more comfortable, in front of you) with the palms facing downwards. (Apologies for this next bit, I work best by feel, so the visualisation here aren't exactly clear). Visualise the palms of your hands as empty black holes, kind of like openings that lead to the rest of your body, now see the edges of these openings rotating clockwise. As you do this, see the Earths' energy beneath you. Now, with these rotating openings, draw the energy up, kind of like the spinning of them is creating a vacuum drawing the energy into your hands.
The first few times you do this, you may only get the feeling of the energy in your hands, but over time it will extend up your arms, and even throughout your entire body, with training. You may feel as though all your muscles are turning hard, your veins being pumped full with rock or magma, any such sensation is normal-for me anyway. These sensations may only move slowly along your arm, the lethargic nature of the earth being the reason, or they may move quickly, the latter hasn't happened to me though.
Oh, and this is really weird to do on a plane mid-flight, you can feel the energy far below you, but it doesn't flow up into you, you just feel the empty space where the energy should be.

Method two:
For this technique it is sometimes preferred to stand up, I am under the impression people sometime visualise themselves like tree for this on, which, as you will see, is understandable.
Anyway, either sitting or standing, clear your mind, and visualise roots extending from your feet/bottom down into the Earth. For me, I visualise these as a light green, lighter than that of the Earths energy. When you feel these roots have gone a comfortable distance into the Earth, begin to draw the energy in, you may visualise it as dark green orbs going up and along the roots, or you may visualise the roots having dark green veins appear on them, or, you might visualise the roots changing to the same colour as the Earth, it matters not, the point is that you should feel energy moving from the roots into you, and filling your whole body.
The feeling of the Earths energy moving into you will be much the same as with the previous method.

Just a small note, if you are capable enough, you can actual induce physical Earth-like attributes, such as the feeling of being made of rock and thus being unable to move which can at times making breathing a tad difficult. Try not pulling so much into yourself that this happens, not very comfortable.

Fire
Common misconception, you can only get this by drawing on the heat energy of a candle, match etc. This is an easy energy to access through visualisation and changing energy from one type to another. Come to think of it all these energies could probably be produced this way, however I have only every found it particularly easy with fire.

This technique was discovered quite by accident and is what got me interested in studying the elemental elements, the inspiration came from a book where a sword was on fire or something like that. This technique is possibly the only one where I suggest using emotion as a power source, for most other things I find calm and a near-apathetic mind frame work best. After all, emotions often induce fire within us, whether they are love or hate.

Using Emotion
Sit in a comfortable position, focus on the emotion you are using, let it consume you, until that emotion makes you feel like you will explode, now visualise your body on fire, the fire running up your arms, across your torso, everywhere, and then push that emotion out into the fire, letting t become the fire, whether it be your love for someone or your hatred for them, let it become the fire energy. When your body starts to heat up and you can feel the fire without having to visualise it, start focusing it in specific areas, such as your hands, which will then naturally warm up.

Clear Minded
Sit in a comfortable position and clear your mind. Now, this is roughly the same as with emotion, visualise your body on fire, but only see the image, don't feel it, we don't want you tricking yourself into thinking you have succeeded now do we? Then push your energy into the image, visualise and feel it taking on the properties of fire. Let it consume you, lose yourself in pushing the energy into the fire until you can push no more, then open up and feel the fire all around you. Again you can localise the energy to a specific area or just let it flow around you and warm your whole body.

This is a very useful way of warming up in winter hehe

I wonder if one could compress this down and really start to play with intense levels of heat... anyone got experiences they wanna share?

Water
Apologies, this isn't anywhere near as precise nor as well researched, as I majorly suck at this and have only tried it a few times.

Water energy comes, surprise surprise, from water, and thus is easily accessed (unless in a dessert). The best water to use is fresh water, I generally use river water because I live right next to one, however fresh rainwater would be just as good, if not better. I can't seem to find any of my sources for what water is related to, however I am pretty sure it is related to emotions and peace/calm.

I only have one method for accessing water energy and it is a little sketching, so try and improvise where things don't seem quite right to you.

If you live near a large body of water such as the ocean, a river, a lake etc then go and sit near it, if not get a bowl of fresh rainwater. Sit in a comfortable position, relax and clear your mind. (This bit is hard to explain) If possible, touch the water, if not then touch it with your energy, now draw the energy into you, whether it be through your hand or attached to your energy, let it flow into you, open yourself up and let the water balance and calm you. Water, as the opposite of fire, will generally cool you down, both physically and emotionally. If you where to use this energy in a ''spell'' it would probably be best to use it so it would pacify someone.

Sorry for the poor wording of this, I am trying to get the scraps of knowledge to make something comprehensible to everyone, which is rather hard for me.