Stand up straight, with chin level and neck, back and shoulder muscles relaxed. Good posture will make it easier for you to correctly use the various muscles needed for singing. It will also help you maintain the proper position and placement of your head, neck and jaw that make proper vocal technique possible.
Use proper breath support. This is the foundation for your tone, pitch and volume. Practice and master delivering all your vocals on a steady stream of smoothly and gradually exhaled air, aided by the diaphragm and abdominal muscles. Control your exhalation, making sure it isn't done so quickly that you can't make it to the end of a phrase without inhaling.
Practice correct vocal technique. Make sure your jaw is relaxed, your throat open and your voice properly centered. When singing correctly, your notes will flow unrestricted through the wide open space you've created at the back of your throat. They'll also resonate inside the mouth, as well as the nasal and sinus cavities (called the "mask" or "masque"). This will make it possible for you to sing loudly without harming your throat or vocal cords, though proper technique will allow you to sing at any volume you choose.
Project your voice. Direct your notes forward (into the mask). This will cause the lips to vibrate slightly and help you sing with increased volume. To locate that forward placement, try humming until your lips begin to vibrate; then switch to singing a different vowel at the end of each hum, maintaining the vibration. Recreate that vibration when you sing.
Remember that singing loudly isn't the same thing as screaming, shouting or yelling. All three strain your throat and vocal cords and are harmful to your voice. When using proper technique, a female singer can belt out a number with absolutely no adverse effects to her voice. So, if you feel any discomfort while singing, stop. Don't try to push your voice beyond its natural limits; if your throat hurts after a practice session, take that opportunity to figure out which technique you need to improve after you've given your voice a rest.