Sliced cooled, hard-boiled eggs in half vertically.
Scoop out the yolks and place them in a small. I use a baby food spoon for this and it makes the job so easy!
Use a fork to mash up the yolks until no big chunks are left. If you're going to pipe the deviled egg filling into the whites later, you'll need to make sure they are mashed up VERY well so that your piping bag doesn't clog. If you're using the baby spoon method you have a little more wiggle room.
Add mayo and dry mustard and mix well using the same fork.
(optional) you can add salt and pepper to taste at this point, but I didn't feel like my deviled eggs needed it due to the mustard flavor and the sodium in the mayo
Spoon (or pipe) filling into egg whites.
Sprinkle with paprika and serve chilled.