TIGGERSMOM, I couldn't agree with you more!!! There should be some sort of contract between cashiers and customers!
I must add to my list though, Do NOT tell me my computer has added wrong if you are the same person who 15 seconds ago could not tell me what 50% off of $10 is!!!
I do see it from both angles though. I hate when a cashier acts if them having to actually do their own job is an inconvenience. However, if the customer is making unusual and/or unrealistic demands, and giving an EXTREME attitude, don't expect that the cashier is going to smile through it (although I do tend to smile through it and be overly polite, it seems to irritate those nasty customers even more, because they feel they're not getting to me). But I do believe that if the cashier is in the wrong, or gets an attitude for no reason, the customer has every right to be annoyed, and SHOULD report it to the manager. Bad customer relations cause customers to not come back. If you feel as though something is wrong, and the cashier will not rectify the situation, don't hesitate to ask for a manager. Half the time, the cashier will give you what is right, and the other half, the manager will. But don't expect to get a $40 sweater for $10 because there was some lint on the sleeve!
So in conclusion: (haha I feel like I'm writing a term paper)
Cashiers: Drop the attitude, the customer is always right (unless they are slightly insane and/or throwing things)
Customers: Understand that the cashier is not responsible for incorrect signage (but can, SHOULD, and is supposed to give you whatever the sign advertises), but if they get nasty, speak to someone in charge.