Yeah, I was going to post some simple der adjustment links and advice, but I think it's best to let your mechanic show you how to do this in the future. After he/she shows you and you pay for the adjustment, I advise you to take the bike off the stand, loosen the cable clamp and loosen the frame clamp completely, then start from scratch on your own, so you'll know how to do everything. (Do this practice while you're still in the shop)

Align der (up/down and rotation)
Set lower limit
Adjust cable
Set upper limit
Test and minor adjust cable