I always use 100 watt bulbs- as many as are needed to get the correct temperature under the lights.
I buy brooder lamps from Home Depot for $12 (ceramic socket ONLY as they last much longer and are safer). They also have them at the feed store for $20.
I hang them at least TWO ways not including the clamp with metal wire. An earthquake would not bring them down.
I carefully check the temperature under the lamps (I have used up to three in the garage, in the coldest part of winter).
Inside the house, one lamp is usually sufficient. Make sure they are around 18 inches above the chicks.
The heat lamp bulbs are dangerous. I had one explode for me once, outside under a tarp in the rain.