1) You're hot, want to party? Please don't go there! It's a place of business, not a meat market.
2) Any sentence starting with "You should have..." This is usually the start of a long monologue in which the customer service representative explains why the customer is the cause of the problem at hand. For example, let's say that Joe ordered an item from your catalog. He entered the item number correctly and did not enter a description for the item. The pickers misread the item number (Joe doesn't have the best handwriting!) and shipped the wrong product. It's not helpful to tell Joe that he should have entered a description or written more neatly. Joe doesn't really want an explanation of what happened, he wants to have the product he ordered.
What's a better way to handle this? Be cheerful and friendly about exchanging the product and making sure Joe is satisfied. Once Joe is happy, you can easily suggest that it would help you avoid these errors in the future if he could also complete the description on the order form so there would be a way to double check his order. Now, you are requesting Joe's help in providing better service and he is much more likely to comply and not to be offended. When you start off by saying "You should have..." you are putting the blame on Joe instead of helping him solve the problem.
3) "I don't know!" I once asked a sales clerk in a large discount chain store if they sold swim goggles. That's the response I got. Then the employee walked off and left me standing there. I left the store and made my purchase somewhere else. Do you really want to leave the customer thinking that you must not be too bright if you can't answer questions about your own business and on top of that leave the impression that you don't much care if they find what they're looking for?
4) "We don't carry that here." That may be true, but let's provide a bit better service. Here are some options: Suggest an alternative product that might work just as well or better, offer to special order the product, or refer the customer to a store that does carry the item. Be remembered for excellent service and the customer is more likely to keep checking with you first to meet their needs.
5) "No problem." This goes without saying. No customer ever thinks of themselves as a problem. Try "It's my pleasure" or "I'm happy to help" instead.