Taken from Mary Ellen's Best of Helpful Hints.

Aphids & Spiders: Wash total plant off with mild detergent and water.
Black Flies: Combine 1/2 tablespoon of plain ammonia and 1 quart of water.
Water soil.

White Flies: Mix 2 tablespoons of dishwashing liquid in 1 gallon of water
and spray on leaves.

Scales: For instant removal of slugs, place plant in pot of water.
Pest of all kinds: Plant a garlic clove along with your plant. As it grows,
simply cut it down so it will not disturb the appearance of the plant.
Garlic will not harm the plant, but the bugs hate it.