1. The Reiki Power symbol - Choku Rei
(Choku Rei is pronounced: "Cho-Koo-Ray")
Some uses:
Increase the power of your healing abilities; use it as a light switch. (Draw or visualize Choku Rei in front of you or draw it in your hands if you want.)
You can focus the Reiki energies (like a looking glass) on a specific point of the body. (Draw the symbol directly on the spot being treated.)
Increase the power of the other symbols. (Draw it before drawing the other symbols.)
One can use the Power symbol to close a space around the receiver and to stop the energies received to disappear from the body. (Draw it above the body with the intention of sealing the healing process.)
The Power symbol can be used to spiritually clean a room from negative energy, to leave it in light and make it a holy place. (Draw or visualize the symbols on all the walls, ceiling and floor with the intent to energize the room.)
You can clean crystals and other objects from negative energies. (Draw the power symbol above or on the crystal/object with the intent of cleansing it and restoring it to its original state. Hold the object in your hands and "give" it Reiki (or send it Reiki from a distance if it is too big to hold).)
Protect yourself from negative energies (from people you treat or people you meet). (Draw or visualize the Reiki Power symbol in front of you with the intent of being totally protected.) You can read more about this on my page about the "Aurashield".
Protect yourself, your children, your spouse, your house and other things you value. (Draw Choku Rei directly on the object/person you want to protect with the intent to protect him/her/it from harm.) Since Reiki works on all different levels of existence it will naturally also give protection on all levels of existence.
These are just a few uses. You can use your own intuition and imagination to find other uses for the Reiki Power symbol – Choku Rei. There are no limits to what you can do. The power is all in your mind, let your clear intention guide the function of the symbols.
The symbol can be used any time during a treatment but it is especially effective if it is used in the beginning of a session to empower the Reiki energy or when used at the end of a session to close the session and seal off the Reiki energies.

2. The Mental/Emotional symbol – Sei He Ki (Sei He Ki pronounced as: "Say-Hay-Key")
This symbol can be used to help with emotional and mental healing. It balances the left and right side of the brain and gives peace and harmony. It is also very effective on relationship problems. The Sei He Ki symbol can also be used on diverse problems like nervousness, fear, depression, anger, sadness etc.
Some uses:
The symbol can be used to help heal misuse of drugs, alcohol, smoking etc.
Sei He Ki can be used to lose weight.
The symbol can be used to find things that you have misplaced. (Draw the symbol in front of you and ask for help in finding xxxx. Let go of trying to find the object. The answer will soon pop up.)
Sei He Ki can be used to improve your memory when reading and studying. (Draw the symbol on each page as you read it with the intent of remembering the important parts.)
Add the symbol when doing healing (normal or distance) as this can help the healing process. Many physical problems have mental/emotional roots.

3. The Reiki Distance Healing symbol – Hon Sha Ze Sho Nen
(Hon Sha Ze Sho Nen is pronounced as: "Hon-Sha-Zee-Show-Nen")
The Distance symbol can, as its name implies, be used to send energies over a distance. Time and distance is no problem when using this Reiki symbol. Many practitioners consider Hon Sha Ze Sho Nen as the most useful and powerful symbol. The use of the symbol gives access to the "Akashic Records", the life records of each soul and can therefore be used in karmic healing. Trauma and other experiences from this life, previous or parallel lives that affect and mirror peoples' behaviors can be brought to light and released.
Some uses:
Send Reiki healing to people far away.
"Beam" Reiki to people across the room.
Send Reiki energies to the future to help with a specific task or be there as a support.
Send Reiki to the past to lift up, to understand and release trauma.

4. Dai Ko Myo https://reikirays.com/15113/dai-ko-myo-explained/
The Dai Ko Myo in Usui Reiki is known as the “Master” symbol. It is one of the most powerful symbols in Reiki that can be used only by Reiki Masters. The power of the Reiki Master symbol combines the power of the first three symbols, Cho Ku Rei, Sei He Ki and Hon Sha Ze Sho Nen.