This classic, simple exercise from Men's Health is a great way to start building your body resistance. The video also gives great tips for your chest-toning progression.
Grab parallel dip bars and use your legs to boost yourself up so your arms are straight and all the weight is resting on your hands. Keeping your elbows tucked close to your body, slowly lower yourself by bending your elbows for a count of six seconds.
Your upper arms should be parallel to the floor at the end of the move. Place your feet on the floor to boost yourself back up and repeat.
As with the negative chin-up, this exercise helps you get used to lifting your body weight if you are not yet strong enough to push your self up. As with a full dip, the negative dip will work your chest, triceps and the front of your shoulder. Exhale as you lower yourself and breathe in as you boost up to the starting position.