Slice the hard-boiled eggs in half longways and line them up in a plastic container or 9x13 pan. Then, toss all of the egg yolks into a Ziploc bag. (A quart-size bag would probably be fine for most families, but I used a gallon-size bag!) Sprinkle some salt in there, too, and carefully squeezing out the excess air, seal the bag. Then, just squeeze and knead the plastic bag full of yolks until they are all mashed up. (This is a perfect job for one of your willing helpers!)
At that point, open your Ziploc bag and toss in whatever ingredients you like in your deviled eggs. Everyone seems to have their own unique family-favorite recipe. We like ours plain and simple -- no "strange" ingredients! So, what I do is squeeze in a squirt of mustard (not too much), lots of Mayo made with olive oil, and salt (if I didn't remember to add it earlier). Then, I carefully squeeze out the air again, and reseal the bag. Find your helper (if her or she wandered off!) and squeeze that bag again until all ingredients are thoroughly mixed together. If you're not sure whether you have enough mayo, open the bag and stick in your pinky and take a little taste! ;) When it passes the taste test, reseal the bag, and proceed to the next step.
Expert Tip: If you are transporting your deviled eggs to a church fellowship meal, family picnic, or to grandmother's house, try carrying your egg whites in a container unfilled. Keep your filling in the Ziploc bag and just fill your eggs when you get there. Don't forget to pack your paprika or other garnish. You will end up with a tray of Perfect Deviled Eggs, instead of . . . well, you know what you get when you travel with a tray of deviled eggs! ;)