There's an art form to a lot of breeds - careful work to make it look like nothing has been done.
On the shelties start with paws, then on the front legs, the feathering from the paw up to the carpal pad. On the sport dogs I just trim it pretty straight and then blend at the carpal pad with thinning shears, but for a show groom you typically cut back at an angle to blend the feathering in with the rest of the leg (when brushed straight, the hair from the lower leg and the top will almost form a triangle at the carpal.)
The hocks you trim up straight to the joint. For show the current trend is to leave quite a bit of fur, it looks very fuzzy, and they blend it down and around into the paw. On the sport dogs, I start at the paw and angle up rather than the more rounded look, and I like a clean, smoother look instead of the more "fuzzy" show look. The hock is supposed to look straight and strong... IMO the smoother look I prefer appears stronger, while the fuzzy makes the leg look fat. Ring trends. Meh.
The ears are the biggest task, the most time consuming IME... you trim out the hair in front of the ear and around the ear. You trim the top of the ear where the break is. The shape of the ear should be rounded in appearance, not a triangle. On the back the ears should round neatly into the rest of the head. LOTS of trimming, shaping, thinning, brush again, thin some more, trim some more, brush again.
This is a big PITA, and to be honest I prefer the more rock star look on my boys... it suits them. So since nobody is going in the ring, they really get minimal shaping on the ears and head. Georgie gets major wild hair on top of her ears, so I trim down the break on her. I do Payton's break as well but only as part of a full groom - Georgie gets it as needed because it looks ridiculous on her. I don't really bother with the break on Pepper or Auggie.
For the face, the muzzle should be clean and smooth, so most just cut the whiskers off. I don't remove all the whiskers on mine; I DO trim off the whiskers on top of the muzzle that curve backward, I trim any whiskers that are really REALLY long, and I clean up their lips. No mustaches or beards allowed on any of mine and ESPECIALLY not on my bitches. I also take off the whiskers above the eyes, the cheeks, and the chin/throat area.
That's it of the normal stuff, and doesn't address any additional shaping people might want to do (some people will shape the hind end, the ruff - V.E.R.Y. carefully - or the underbelly) or anything that might be done to disguise flaws in the dog's structure.
It's actually a pretty time-consuming process to do a full show groom and the key is to make it look like you didn't groom at all. Everything is supposed to flow and blend together seamlessly. Just say NO to scissor marks!
That's one of the big reasons I won't let anybody else scissor my dogs. It shouldn't look like they got scissored. And clippers really shouldn't get anywhere near a sheltie IMO. Scissors will do everything you need so long as you know what you're doing... and are careful.
ETA: I should add that a bath, blow-out, and full groom on all of mine (including Georgie) takes about four hours. P usually takes the longest, although sometimes Auggie doesn't drop his coat easily and requires more line-brushing. The girls are the fastest, especially Georgie who is mercifully tiny. If I started doing ears/heads, I would probably add another hour at least... UGH.