How to make your breast firm without actually carrying weight?

1. The Modified Push Up

Lie on your stomach, bend your knees, and cross your ankles. Bend your elbows and place your palms on the floor a bit to the side and in front of your shoulders. Straighten your arms and lift your body so you’re balanced on your palms and knees. Tuck your chin a few inches toward your chest so your forehead faces the floor. Tighten your abdominals. Bend your elbows and lower your entire body at once. Rather than trying to touch your chest to the floor, lower only until your upper arms are parallel to the floor. Push back up. Don’t lock your elbows at the top of the movement and don’t do the dreaded “head bob.” That’s when you dip your head toward the floor without moving any other part of your body.

2. Soup Can Press

Lie on your back with your feet flat on the floor and a soup can or dumbbell in each hand. Push the soup cans up so your arms are directly over your shoulders and your palms face away from you. Pull your abdominals in but don’t jam your back into the floor; don’t let it arch way up, either. Tilt your chin toward your chest. Lower the soup cans down and a little to the side until your elbows lightly touch the floor. Push the weights back up, taking care not to lock your elbows or allow your shoulder blades to rise off the floor. (Note: Use soup cans of equal weight. When those get too light, you can fill two Pinesol bottles with dried beans or pebbles.)

3. Incline Fly

Lie on the floor with your head, neck and upper back propped up against several large pillows. Hold a soup can or dumbbell in each hand and press the weights directly above your chest, palms facing each other. Tuck your chin to your chest to align your neck with the rest of your spine, and maintain your natural back posture, neither arched nor flattened. Spreading your arms apart so that your elbows travel down and to the sides, lower the weights until your elbows lightly touch the floor. Maintaining a constant bend in your elbows, lift the weights back up, imagining that you have a barrel lying on your chest and you have to keep your arms wide to reach around it.

hope this helped ;]