Don't let my previous post fool you. I haven't always hired the right people. I've hired some real lemons in my time.
Some you can tell almost right away, some wait till just after their probationary period and some turn on you when their environment changes. Things like theft and tardiness are obvious firing reasons.
I've had a few girls when confronted with minor correctable problems freak out. It'd be funny if it wasn't so sad. Instead of correcting their mistakes they make the situation worse by denying it or trying to blame the person who they think snitched on them. All they had to do was correct their mistake, instead of obsessing about getting caught. When this happens there's not much I can do but to let them go.
Probably the trait I can't handle most in employee is harmful gossiping.... oh gossiping about boyfriends or how something makes someone looks weird is fine. It's the harmful work gossip I can't handle. When I find it, I do my best to stamp it out. I never discipline staff on the basis of what another staff says. I always observe it first hand myself before something happens. I do usually give one warning. However, I will surely fire someone if they think they're indispensable. I value all my staff but let's face it everyone is replaceable.
There are rare times when I've been able to turn lemons into lemonade. Those staff have been in my experience some of the best staff I've had the pleasure to work with.