I make these for every family dinner and for most other parties and barbecues as well. Mine are a bit spicier than others - the key ingredient is the cumin. Don't leave it out, because it's what makes these so delicious.
For the seasoning salt, I like to use Herbamare or Tony Chachere's, and for the mayo, Duke's or Hellman's is preferred.
Regarding the eggs - for my hard boiled eggs, I use eggs that are a week old. There is nothing wrong with week-old eggs (provided they have been kept refrigerated), and they have the delightful quality of being peelable, unlike their fresher sisters.
NOTE: if you plan on filling these by using a cake decorating tip, make sure the pickle and green onions are very finely minced - you might want to run them through a food processor or blender to get them fine enough. Otherwise, they could clog up the tip. Also, the garnishes listed below are all optional, so use at your own discretion. Most people don't use caviar unless they're trying to out-fancy someone else. I personally prefer chives.
Ladies and Gentlemen, get out your deviled egg plates!