This is a wonderful resource from MyPetChicken.com for new chick owners:
http://www.mypetchicken.com/backyard-chickens/chicken-care/guide-toc.aspx
This excerpt is from Chapter 4, "Caring for Chicks"
"A heat source
Baby chicks need to be kept pretty hot. Think sauna! The first week of their lives they require an air temperature of 95 degrees, the second week 90 degrees, and so on - going down by 5 degrees per week until they're ready to transition to "outside". A 250-watt infrared heat lamp is the best way to achieve this, placed right in the middle of their living area and suspended off the ground. The height of the light will depend on what it takes to achieve your target temperature.
We recommend a red heat bulb for a few reasons: one, with a bright white light constantly glaring it can be hard for them to sleep. The red light is darker and provides them some respite. Two, red lights help prevent them from pecking one another. We sell both red and white heat bulbs plus the brooder lamps.
Pay close attention to how your chicks behave. If they're all crowded together directly under the heat source, they're cold. Lower the heat lamp or add another one. If they're around the edges of the brooder, avoiding the heat and each other like the plague, they're too hot! Raise the heat lamp. A happy flock will happily be exploring all around the brooder.
And please do not listen to anyone that tells you a regular old 60 watt bulb will suffice! We've seen chicks die from this bad advice.
They really need a lamp intended to produce heat, and as we've mentioned, we recommend the 250-watt variety."