Have ready a large bowl of ice water (known as an ice bath), a slotted spoon, and a plate lined with a cloth or paper towel.
In a large pot, pour 1 or 2 quarts of water and bring it to a boil. When the water is boiling, carefully drop the fruits or veggies in, immersing it.
You can prepare the vegetables or fruits by cutting them just before the blanching process to prevent oxidation. Cut them into uniform pieces to ensure even cooking.
Add 1 or 2 tbsp of salt (add 1 tbsp per 1 quart) to the boiling water. Adding salt maintains the color and helps improve the flavor of your veggies (this is optional).
Add veggies in small batches, this way the water continues to boil. If blanching more than one type of vegetable, blanch each one separately and blanch lighter colored ones first, as darker colored ones will tinge the water and subsequent vegetables.
Test for doneness after 30 seconds by removing one piece, dip in the water, and taste. Keep tasting every 30-60 seconds until the vegetables are cooked to your liking. Most vegetables take between 2-3 minutes.
Once they are done, quickly remove them from the boiling water with a slotted spoon and plunge them into the ice bath to stop the cooking process. (This is called "shocking.")
When the vegetables are completely cool, remove them from the ice bath and drain on the towel-lined plate.