This instructable will show you how to tune up your front derailleur. This is a quick process that shouldn't run more than 20 minutes.
Step 1: Tools
You will need a set of allen keys and a screw driver.
Step 2: Height
First thing to check is that the derailleur is in the right spot. Shift to the big ring and see if the derailleur cage is just a few millimeters above the teeth of the big ring.
Step 3: Height
If not, then loosen the cable, and adjust the height by adjusting the clamp that holds it on the seat tube.
Step 4: Straight
You want the cage of the derailleur to be lined up perfectly with the teeth of the front chain rings.
When you tighten the clamp on the front derailleur you will notice it pulls the cage in towards the wheel, you want to compensate by turning it out a little from the wheel before you tighten.
Step 5: Limits
Now with the cable still off of the derailleur you want to set the lower limit.
the lower limit keeps the chain from falling off the chainring and on to the bottom bracket shell.
First thing to do is shift in to the biggest ring in the back and leave the chain on the small ring in the front.
Step 6: Limits Continued...
Now that you have the chain on the big ring in the back, its time to set the limit screw on the front derailleur.
The screw closest to the frame usually adjusts the inner limit, but if not just use the other one...
Trim this screw so that the chain is just barely not rubbing on the inside of the cage.
Step 7: Cable
Now attach the cable.
Step 8: Shift...
Now shift to the big ring in the front and small ring in the back.
Step 9: Trim
Trim the other limit screw so the derailleur cage is just barely not touching the chain.
If the limit is out to far it will pop over the big ring and in to the cranks while you are shifting... no one wants that.
Just test it out and you're good to go.