I got this hack from Cooking Light magazine. Place the sliced onions in water for 10 minutes. It will take away the bitterness of the onions. It actually worked. Not sure if it would do the same for white and yellow onions.
Chopped garlic is used in many recipes. While a garlic press is a useful tool a shape knife and cutting board will work just as well. Watch a short video showing how to finely chop garlic cloves without a garlic press.