What is the most effective way to decrease a child's fever?

Medication. A fever does not always need to be decreased. However, if your child is uncomfortable, there are things you can do to relieve that. Tepid baths or cool compresses to the forehead, inner arms, wrist, and/or neck. If your child is older than 6 months, you can use medications that decrease fevers. Acetaminophen (tylenol) or ibuprofen (advil, motrin) both work well. Always dose by weight, not age.
Why. Fever is the body's way of defending against viruses & other diseases & in & of itself is a symptom not a disease and should not b lowered unless very high. Get a DX from ur pediatric md & then follow his directions.