Incline bench press is the bench press' ugly second cousin.  People know it exists, they just care to focus on the familiar bench press.  That's too bad, because it is your upper pectorals that give your chest a lot of volume and upper body power.  You would be wise to include this exercise in your routines.

Starting Position

Incline your bench to no more than 30 degrees (usually the second hole on the adjustment bar).  Load your barbell and put it on the rack with sufficient weight.  Lie on your back on the bench under the bar with both feet planted firmly on either side of the bench.  Your butt, back, and shoulders should be in contact with the bench.  Reach up and grasp the bar with an overhand grip slightly wider than shoulder width apart.

Performing the Exercise

Much like the bench press, you push up on the bar lifting the bar clear of the rack.  Then you lower it under control until it slightly touches or is slightly above your chest.  Hold for a second, then push the bar back up extending your arms, but do not lock out your elbows.  You will notice that your elbows stay closer to your sides for this than they do for a regular bench press.  Be sure to bring the weight down to your chest and not to your neck.

Tips

Keep your back, butt, and shoulders on the bench at all times.  Lifting your butt off the bench is like decreasing the incline angle which has the effect of turning the incline bench press into simply a bench press which will then target the wrong muscle.  As well, ensure that the angle is no more than 30 degrees or you are going to target the shoulders more than the chest.  When in doubt, lower the bench if you want to hit your chest.  Work the upper pecs just as hard as the lower ones and you'll start to fill out that T-shirt a lot better.  You will also notice more zip in your punches.