Use correct posture, which includes a slight bend at the hip sockets and knees. This gives you better use of the lower abdominal muscles for breathing, which prevents you from breathing below the rib cage. Align your ears with your shoulders to help relieve strain on your neck.
Keep your tongue flat and raise your soft palate as you attack your vocals. This, in conjunction with proper use of the diaphragm, will help you project your voice. Since the bass voice is more difficult to project, using this combination of techniques can make you bass vocals stand out.
Practice singing scales based around the middle voice F natural. Use open vowels in the lower vocal register and switch to rounded vowels as you reach the higher register (see resources). The traditional "do, re, mi, fa, so, la, ti, do" scale contains a mix of both types of vowels. It's an acceptable way to vocalize a scale, but combine it with scales that rely on one type of vowel or the other.