Too true! My LFS will hold a fish for a couple of weeks without me putting any money down. I come in and inspect the fish maybe every 5 days or so to make sure it's doing well. One of the biggest mistakes I made as a newbie was adding my yellow tang as one of the first fish.
Our sister site MFK has a forum called Lessons Learned. I check in time to time and there's a lot of good advice there. Wouldn't mind seeing a thread here with a 'Lessons Learned' theme. I'm sure we all have a story or ten- even if it was years ago.