Although store bought rooting compound doesn't seem to be overly expensive, most folks don't know that it can be toxic due to the fungicide included to protect plant cuttings from disease.
Just as in humans, hormones stimulate various functions in plant growth. The first hormone discovered to cause root growth is called auxin, and the synthetic version of auxin is what we find in commercially sold compounds today.
The willow plant is a natural source of auxin. Therefore, it can be very easy to make up a fresh batch of homemade rooting compound whenever you need to plant some new cuttings.
Gather a handful of willow branch tips
Chop or mash into smaller pieces
Fill small container with pieces
Fill container with water & allow to sit overnight
Remove willow pieces
Dip cutting into the water, covering the stem
Put cutting into your potting mix (or moist sand)
Cover with a plastic bag to retain moisture
After roots form, re-pot
Also, don't get rid of the willow water when you're done with your cuttings. Save it to water your plants!
If you don't have access to willow, dissolve a few aspirins in a jar of water. Aspirin is made from willow bark, so it can have the same effect as the willow water.