How can I tell if citrus fruits in the store are fresh and of superior quality?

Citrus fruits do not continue to ripen once they are harvested, so be sure to choose firm, smooth- skinned, shiny, and brightly colored specimens. Avoid fruits with soft spots, bruises, and discolored skins. Heavy, thinner-skinned citrus fruits tend to be juicier than light, thick-skinned fruits. A very rough peel is generally thick--a sign the underlying fruit may be small and dry.
 
The fruit should impart a faint, sweet fragrance at room temperature.
 
Choose grapefruit with bright, smooth, thin and unblemished skin. Grapefruit that is heavy for its size will be juicier. The grapefruit should be springy to the touch rather than soft or wilted. Surface defects such as scars, scratches, and discoloration don't affect flavor.
 
Look for firm lemons that have a glossy, bright, yellow color. The skin should also have a fine-graded appearance. Ripe lemons should feel heavy for their size. As with grapefruits, avoid specimens that are hard or spongy and soft.
 
Limes should be firm, glossy, and bright in color. Persian limes should be a dark green. Key limes should be pale green to yellow. For the juiciest limes, select ones that are heavy for their size.  Again, avoid limes that are hard or spongy and soft. Limes should, however, have some give.
 
When selecting oranges, look for fruit with a shiny skin that is free of blemishes, wrinkles, soft areas, or mold. Oranges that are heavy for their size are juicier. Select navel oranges with small sized navels. Oranges with larger navels indicate the fruit was overripe when it was picked.
 
Choose tangerines or mandarins that have deep, glossy, orange skins and that are heavy for their size. These fruits will feel soft and puffy compared to oranges because of their looser skin. Don't worry about small green patches you may see near the stem end. 
 
Source(s):
Metro Grocers "Citrus Fruit"
Whole Foods "Guide to Fruits"
Ehow.com "How to Choose Citrus Fruit"
Tonytantillo.com "Produce Tips: Fruits"