I THINK you're supposed to reduce temp by 5 degrees each week. I wound up just watching the chicks and adjusting temp based on behavior: avoiding lamp = reduce heat, all under lamp = increase heat, everyone wandering aimlessly = just right!
I use yellow bug lights, I use a 100 watt for the first few days then Change to a 60 watt for 2/3 weeks then a 40 watt for 2/3 weeks then they just get used to my house temp for a week or so before moving them out side.
If they are panting lower the bulb size.
If they are crying and trying to get under each other raise the bulb size.
If its cold out when I move them to the coop I will give them a heat lamp again.
Please note that your chicks will need a source of heat until they are fully feathered. Most chicks are not feathered out until 8 - 10 weeks of age. Some breeds are not feathered out until closer to 12 weeks. It is this feathering that allows them to regulate their own body temps. With very young chicks like yours they need the warmth the lamp provides them and they need it constantly. They need a brooding area big enough that when they are too warm they can move out to the edges of the light to cool down. If too cool they will move under the light to warm themselves. Week one under the light should be 95 degress. Week 2 - 90 degrees. Week 3 - 85 degrees. Week 4 - 80 degrees. Week 5 - 75 degrees. Week 6 - 70 degrees. Around this time you can start weaninging them off the light if temps permit. On warm sunny days they won't need the lamp but will stiull need it during the cooler night temps. If your chicks get cold they could get sick. It is very hard for a chick to recover from getting sick. Being cold can be fatal to them. Chicks are tough little boogers but they are also very fragile.