Here are directions from the Georgia Department of Natural Resources (GA DNR) on how to make the best and healthiest hummingbird feed:
The best solution consists of one part sugar to four parts water (this mirrors the sugar concentration of the nectar found in flowers).
Boil the water for 2—3 minutes before adding sugar. Cool and store the mixture in a refrigerator until you are ready to use it.
There is no need to add red food coloring. Hummingbirds are attracted to the red color of the feeder and do not prefer red nectar to clear.
Select a feeder that is easy to clean and does not drip. In warm weather, change nectar every two to three days or before it gets cloudy.
Periodically clean feeders, making sure that mold and bacteria are removed
Feeders can be easily cleaned by soaking them in a solution of one part bleach and 10 parts water.
Thoroughly rinse the feeders before using them again.