Clean the feeder every 3-5 days with hot water. Vinegar can be used if necessary. Excess nectar can safely be stored in the refrigerator. Ants in the feeder can be avoided by using an ant moat over the feeder. This commercially available plastic cup is filled with water, which prevents the ants from gaining access to the feeder.
Bees can also be a problem.
There are certain feeders that are bee resistant. Feeders that have feeding ports above the nectar can be partially filled so that the bees can't reach the nectar sorce. For other styles of feeders, you can try applying a small amount of petroleum jelly where the bees are clinging. For those who want a lifetime warranty, this is the company name to look for no matter which birds you are trying to attract. UV stabilized, impact resistant plastic, nectar recipe engraved on the top, built in perch, low profile for unobstructed viewing, a small port brush, and of course, the lifetime warranty.