Being a good Subway customer not only makes the process much faster, but it also makes the employees happier. In return, you will get a better quality sub, and a more friendly service. Follow these steps, and it will make everyone much happier.

[edit] Steps

Be prepared by knowing what you want to order. Inform them if you have any coupons, or if you are taking advantage of a sale.
Start by telling the employee how many, what size, and what type of bread you want. "I'll have one foot-long on sourdough".
Note that, after they have the bread out and cut, you should inform them what type of sandwich you want, what kind of cheese, and if it is to be toasted or not. Ex: "I'd like a BMT with provolone, toasted".
Answer the mayo mustard question after it is asked. Be specific as to type of mustard. "I'd like light mayo and honey mustard".
Do not start to tell them what kind of vegetables you want until the employee asks you what you want on it. The employees will ask you when they are ready.
Let them know if you want anything else. This includes crushed pepper, oil, etc.
Inform the cashier of any last-minute purchases. This goes for cookies, beverages, soups, and meals.
Refrain from talking on your cell phone. This is quite rude. The call can wait until you are finished ordering.
Be courteous. Let others go ahead of you, if you are uncertain what to order. This will make the line alot faster.

[edit] Tips

Please do not complain about the lack of meatballs. After 7:00pm or so, they are thrown out because they have been sitting all day.
Try not to come within fifteen minutes of closing, out of common courtesy.
Do not stay in the lobby near closing, it needs to be swept and mopped before the employees can leave.