So we have a general hierarchy established in the story:

Alicorns
Unicorns
PegaI
Earth Ponies
Other sentient species

So what awkward things come up at say... a meeting at a cafe. If the Mane six get asked what the want to drink is the order of: Twilight, Rarity, Rainbow or Fluttershy, Pinky or Applejack?

Thoughts?

4510583

Twi, Rarity, RD (because she's an invasive bitch), Flutters (only because all eyes will be on her), Pinky (because she couldn't keep her mouth shut), then AJ (because shes probably the most sensible of them all). Though it's entirely possible that Pinky would butt in with what she wants first, along with RD. Other ponies would probably just view them as crass and a bit trashy.

PegaI

I love Pegals!

I am sure that drink-serving based on a hierarchy only happens in Canterlot. That could not happen in other areas of Equestria. There might be some up-tight sticklers who insist serving in that order.