Lie down on a flat bench and grasp the barbell a little past shoulder width.
Unrack the weight and lower the bar in a controlled manner until it almost touches your nipple line. Then, return to the start position and repeat the movement for the desired or prescribed number of repetitions.
Lower the weight in a controlled manner
Perform the exercise in a smooth and fluid motion
Don't arch your back as this may result in injury and it also shortens the span of the exercise movement
SPECIAL NOTES & LEVEL of DIFFICULTY VARIATIONS
If you want to increase the level of difficulty, just load the bar heavier. If you are having problems with arching your back, try raising your legs (bent 90 degrees at the knees and crossed at your ankles) and perform the exercise like this. However, this is for advanced people who can maintain their balance well while doing the bench press in such a manner.