This is a cool website with lots of tips and tricks from people. My favorite is from a Sandwich Enthusiast:

When ordering a “custom” sandwich from a deli, Subway, or college cafeteria, say the name of each ingredient with a air of finality, as though it will be the last ingredient on your sandwich. The sandwich-maker will pile plenty of the stuff on, trying to fill your sandwich to a respectable size, not realizing you intend to ask for more ingredients.

Make sure you check the archives for a lot more. [Link]