When it comes to singing, how you breathe is just as important as your pitch. Postural alignment is the first thing to work on. You have to be sure your rib cage is strong, lifted and open, while your breathing needs allow air to get deep into your torso. Use your ab muscles to lift and open up the chest. When exhaling, your ribs should remain lifted and open. This should help with a fuller sound. 
Focus on what you are doing with your tongue, throat, and jaw. Keep your tongue flat, wide, and out of the way. Relax your jaw and mouth in order to allow your voice to project. Believe it or not, smiling while you are singing is helpful; it will relax both your throat and jaw.