Deep-tissue massages focus on relieving tension deep within the body's musculature. To give a good deep-tissue massage, you will need to know the basics of human muscle anatomy, how to properly apply deep pressure without causing pain, and how to identify areas that need more attention. Professional masseuses attend many hours of school and practice their techniques daily. Even without all that training, you can give a pleasant deep-tissue massage by learning the basics.
Familiarize yourself with the basic anatomy of the muscles in the areas that you want to learn to massage. A good place to start is the back. You can find good images of the musculature of the back through the link in Resources. Have these images handy as you practice massaging someone, and try to match the muscles you feel in her back with what you see in the image.
Start a massage by applying some massage oils to the area and running your forearm, positioned cross-wise, up and down one side of the your client's back. Don't push with your forearm, but lean in with your weight and let your forearm slide down the back before sliding it back up. Avoid pushing on bony surfaces as you work, especially the spine.
Use your fingertips or thumbs to probe for individual muscles and the boundaries between them. Begin to apply more focused pressure by leaning into your fingertips or thumbs as you go. Look for tense knots or areas where muscle mobility seems more limited. These are the areas that your client will often say feel tender when you press on them. These are also the areas that require more attention.
Apply greater pressure to knots or tense areas by leaning into your fingertips or thumbs and allowing them to sink slowly into the muscle. Do not push with your shoulders or otherwise attempt to smooth out the knots too quickly. Have patience and allow your gentle pressure to achieve greater penetration into the tissue or you might cause pain.
Check with the person you are massaging to find out what feels good and to make sure you aren't causing pain. Constant communication is a must if you are not a professional.