Fire
Fire is masculine and rules EXTERNAL action. It can be driving and burning. You want fire energy to help you take that first step to making your dream real. It is also indispensable when courage is needed. In love, fire is the element that brings passion--this applies not just to romantic love, but to any pursuit that gives you intense feeling.
The elemental for Fire is the salamander, a dragon-like creature which is sometimes depicted as being aflame, but unharmed. More recently, salamanders have been depicted as being made out of flames. The salamander can be large, or very tiny. An interesting origin story for the legend of salamanders is that real salamanders like to live inside logs. When the logs are tossed on the fire, the salamanders, naturally, run out of the flames. (source) Salamanders symbolize grace under fire (literally, in the salamander's case) and faith that cannot be extinguished (source). You might like to visualize a salamander as a companion during your meditations.
Fire is also cleansing. It can burn away sickness and negative energy.
To bring this courage, passion, and driving force to your endeavors, sit or lie down, and focus on your breath. Just relax and notice it.
Imagine a small fire kindling inside you. This fire starts right in the middle of the area where you sit (your root chakra) and flames through your lower spine (the sacral chakra) and into your belly (the solar plexus chakra). The color of these chakras are red, orange, and yellow, respectively. The red root chakra concerns sexuality (making this exercise excellent before a big date) as well as security, which is necessary for courage and moving outward. The orange sacral chakra is about enthusiasm, creativity, and joy. The yellow solar plexus chakra (so called because it is the center of the body, like the sun) governs personal power, expansiveness, courage, and growth. Visualize these chakras igniting, and the flame moving up the spinal column.
Imagine the fire burning away all negative emotion, all pain, and changing anything that torments you into heat and light. Imagine this heat and light filling every single cell of your body.
Stay in this warmth and light and flame until you feel cleansed and energized.
Fire is useful for healing if channeled as a gentle heat. This is especially nice for sore muscles or frost bite, or just when you're feeling chilly. A good visualization for this is to imagine red, orange, and yellow liquid energy, or light energy, flowing into the effective area.
If fire gets out of control, it manifests as anger and manic behavior. There is intense activity, followed by a crashing burn-out. Physically, this shows up as infections. It is helpful, then, to imagine cooling energy of a green or blue color--either as light or as liquid--and picture it "washing out" and cooling the affected area. If the excess fire is emotional, imagine the entire body filling with this blue/green liquid light.
Earth
Earth lends practicality and patience. It brings abundance and fertility. It moves slower than fire or air energy, with a great payoff. Soil is not the only component of Earth--flowers and trees are also part of the Earth, and so are useful to meditate on.
Earth is a feminine element, and is very nurturing and calm. However, this is deceiving. There is a lot of activity in the Earth and its flora. Think of sap rising, or flowers stretching toward the sun. It takes time, but it is steady, constant change, not the flaring of fire or quicksilver air. It is associated with the Mother goddess, who gave unconditionally.
Earth energy is helpful is you feel adrift and insecure. It is an energy that gives a feeling of safety, so it is also good for anxiety or any other type of nervous energy. It helps you stand tall.
Earth is also very good for transforming painful memories or thoughts into something healing and valuable.
If you're feeling anxious, sit or lie down, and just breathe for a few moments. Simply notice your breath, and how it feels going in and out.
Imagine energy in the form of roots growing down out of your body, and up out of the earth. Imagine these two energies meeting. These roots may be dark green, gold, or pink. You are now connected to the Earth element.
Imagine this energy gently supporting you and enveloping you. It can feel warm, or cool, whatever you need. It wraps you like a blanket or a mother's arms. The energy is also flowing into your body, strengthening you, and giving you power and endurance, like sap in a mighty oak tree. Imagine it fortifying your root chakra, located by your tailbone. Feel your spine lengthen and grow tall.
When you need endurance, visualize this energy traveling up your spine into the top of your head. Imagine yourself growing, growing, growing toward your goal. When the energy reaches the top of your head, visualize yourself having reached your goal. Imagine how wonderful it feels.
Sit in this visualization until you feel warm and secure, or until you have a boost of confidence.
To cleanse and transform negativity, sit and breath as before. Relax. Imagine the negative emotion as something you can see--you may choose to make it a monster, or sludge clogging you. If it is a negative experience, imagine the experience being played on a big movie theater screen. Imagine it shrinking down until it is tiny.
Get the Earth energy flowing through you again. Then, imagine the Earth's roots sucking away the negativity, the tiny screen, the monster, the sludge. Imagine it getting sucked down out of your feet, or out of your back, if you are lying down, and into the Earth. Visualize the healing energy, in the color you chose, being taken into your body through your energy roots.
Now imagine the Earth turning this negativity into soil. This soil is nutrient rich. This soil can now produce positive, healing energy. It has been transmuted.
The shadow side of Earth energy, or a sign of having too much, is sluggishness, lethargy, and depression. Things are stagnant, and there is no motivation. The best way to counter this is to look to the fire and air elements, which are more kinetic. I highly recommend doing the kindling visualization, described in the fire description, or this air visualization.
Lie down or sit with your feet flat on the floor. Pay attention to your breath. Don't force it, just notice it.
This is the element of air. This is what keeps you alive.
Visualize it filling every nook and cranny of your body, every cell. Imagine it filling all the deflated parts of you. Imagine it lifting your chest, your shoulders, and your heart. Imagine it surrounding your brain through your nostrils. Visualize your brain waking up in every cell.
Now, we will go further. Imagine flying on a stream of air. This air supports you and propels you, just like water. Feel it rushing into your face, into your lungs, refreshing you. This air is taking you places. Give yourself the wings of your dreams, if you'd like. Look down. What beautiful scene do you spy rushing underneath you? You have an eagle eye view of it. There are opportunities as far as the eye can see.
Look around you. If you see clouds, or things look murky, imagine a gentle but strong breeze blowing them away.
Tell yourself, I have the energy and foresight to achieve what I want to achieve.
Stay in this space until you feel clear, refreshed, and energetic.
This visualization will be reprinted in Part 2, when I discuss Air and Water.
I highly recommend Caroline Myss's Anatomy of the Spirit for further discussion of the chakras. It is fantastic. It is in-depth, and accessible without being condescending. It's also a fascinating read. It not only discusses the chakras, but the Kabbalah Tree of Life and the Christian Sacraments.