Good screen quality with the type of screen he prefers Matte/Glossy.
Resolution IMO larger the better especially when working on a 1:1 pixel level. If using HD video best to somewhat future proof yourself by trying to get a 1920x1200 LCD to display full 1080 content as well as of course lower levels like 720P.
Graphics card, any low-mid size current GPU would be good, avoid integrated for the most part. Solid ATi X700, 1300, 1400, 1600, HD2300/2400 and HD2600 or else Geforce GF8300/9300 , 8400/9500, 8600 would be fine. Try to go for at least 256MB of memory with a true hard limit of 128MB. Size doesn't matter too much but does help with more complex tasks with layers and transitions.
CPU power is maiinly for applying effects, faster the quicker they happen and the easier previews are, final render for video is mainly CPU & Memory power.
Memory, as much as you can afford, but usually best to go small from mfr and then upgrade yourelf (word of warning though some mfr lock the BIOS to keep you from upgrading yourself, make sure he checks with the mfr that he can upgrade the modules himself with quality matched pairs and doesn't need multi-hundred dollar specialized memory). If they don't give you a good answer on that don't buy from them, cause they'll suck at other support too most likely.
Hard drive is more a question of preference, but the best option right now is a large WD 320GB 5400 RPM drive which is faster than most 7200RPM drives, yet still quiet and energy efficient.