In my recent experience of working at a fast food restaurant, I've come to believe there are five main types of customers. Almost inevitably, any customer that walks through the doors of the restaurant can fit into one (or several) of these categories.
1) The JERK
The JERK is someone who orders his order rather quickly. Usually this person thinks he knows what he wants, but he still has to answer some clarifying questions that he forgot to say right off the bat. For example, he forgot to list the sauces he wanted, he didn't clarify the size drink he wanted and he didn't mention whether he wanted this "for here" or "to go." This person maintains minimal eye contact with the cashier, and when it comes to getting the table marker, he walks away in the middle of the instructions ("Please put this at the edge of your--okay, that's fine, you can just walk away...."). The way this person pays his money also characterizes him as "the JERK." For example, when he pays with plastic, he hands the cashier the card between his two fingers and often looks away. In cash he will make sure to give the "extra change" so his return change comes in the most "complete" form (he does not have time to mess with those obnoxious pennies). Overall, there is a lack of respect and cashiers are only viewed as the medium to get to his little fried meal.
It should be noted that this doesn't exclude women either. Women can be equally as "jerky" (although there are several stronger words I can think of...).
2) The IDIOT
This is probably the single most frustrating person to serve. This person DOES NOT KNOW WHAT HE WANTS. He *thinks* he knows, but he does NOT know how to order it. He thinks he wants three chicken strips with fries, but no drink...and what comes out sounds like he wants the entire freaking meal. It's usually people who DON'T know how to order that get the most frustrated when they are asked to clarify. I don't know why this is--it's a phenomenon I have yet to discover. This is also the same type of person that adds on last-minute orders. However, you have to be very careful when you try to figure out if they're done ordering, lest YOU annoy them more... This type of person usually puts off the strongest "I-can't-believe-I'm-talking-to-this-moron-cashier-who-can't-get-my-order-straight" vibes, and there's no way to let him know IT'S NOT ME.
3) The NICE PERSON
Now, these next two categories are a little more rare, but meeting these people is what gets me through my day. The "NICE PERSON" is the person who orders respectfully, looks you in the eye (not always, but at least once), and the exchange is pleasant and uneventful. It's awesome. They sometimes don't know what they want, but they're still able to eventually order what they want with success. There's not much more to say about them.
4) The DIRECT PERSON
This person knows what they want. They tell me straight up, "This is to go. I want a number whatever with this, this and that and my name is this." Boom, right there. There's NO GUESS work. Bless those people.
5) The PERSON WHO DOESN'T KNOW ENGLISH