Here is my recipe for homemade hummer nectar:
Do not use honey or red dye!
Use a ratio of 4 parts boiling water to 1 part sugar. Cool before filling your feeder. Store any unused syrup in the refrigerator for up to 3 days.
Make sure the nectar is as fresh as possible. Any cloudy nectar should be discarded, the feeder thoroughly cleaned inside, and fresh nectar added.
Place hummingbird feeders in the shade if possible. This keeps the bacteria from growing as fast, contaminating the nectar.

 

Your hummingbird feeders need to be cleaned, and nectar changed every 3-4 days--more often in hotter weather. If you see black spots inside your feeder this is mold and you will need to scrub it out with a good bottle brush, but if you can't reach it with a bottle brush you can add some sand with water and shake the feeder to remove the mold. You should never use harsh detergent to clean your feeder. Rinse out each time you change your nectar with hot water, and if you do this on a regular basis you should not have a problem with mold inside the feeder. Don't fill the feeder more than half full, because they won't be able to drink it all before it will need to be changed.