PUSH FROM THE GUT!!!
Actually, don't push from anywhere. Never push, that will ruin your voice, and you sound shitty while you're doing it.
The number one thing that anybody needs to do when they're singing or playing an instrument is breathing correctly. Before you start warming up your vocal chords, do some breathing exercises. In for four beats, out on a lip flutter, hiss, or later a note for eight, twelve, sixteen, twenty beats and then as long as you can sustain a good flow for. If you're not lightheaded, you're not doing it right. Make sure that when you're breathing, you're doing it into the stomach, and not into the chest. Picture the air flowing down and out in your stomach. Don't be modest about showing any kind of "gut" when singing, it means you're breathing and using enough air.
Also, you need to eliminate tension, especially in the upper body. A lot of people carry their tension in the shoulders and neck. If you can, give yourself a little massage (or find somebody else to give it). Lower your shoulders, bend your knees, don't stretch out your neck, keep your chin down (but don't sing to the floor).
One last note, with any shaping or articulation that you are singing, exaggerate it. It is much easier to pull back on these things than it is to add them.
