Oooh I could go on and on here.
Let's see, the
WORST advice I've heard in an LFS was:
The guy is in the process of buying a second tank to house fish that aren't working out well in his main tank, for whatever reason. I don't remember most of the conversation - but I do remember, quite vividly, this dialog:
Guy: Ok, is there anything else I need to add to the tank besides my filter?
LFS: You should have an airstone and airpump. That gives the fish oxygen, without it they won't be able to breathe.
Guy: Ok. Do I have to let the tank sit for a while first?
LFS: Nah, I never cyle any of my tanks and my fish do just fine. Just add water, and in 10-12 hours, move your fish.
They never cylce their tanks, but the longest they have their fish for is a day. The store is always super busy...they're normal prices are cheap, and they're also "Buy 2, get 1 free" every day. Plus, on Sunday - in addition to the "Buy 2, get 1 free", your fish total is 1/2 off.
Someone posted in here something about this post made it seem like you couldn't trust any LFS. Just for the record, I've been on a LFS finding spree. I've found about 1/2 dozen, all within an hours drive of my house that I'm just in love with. The staff is friendly, knowledgeable and the fish selection is healthy and pretty wide.

Prices are a bit steeper than normal, but you're getting nice quality fish.