I would now like to share with you the way of the slushie/Icee/Slurpee.
Always pound the cup. Slushies are carbonated. This means that they grow...and then deflate. By the time you get to the counter to pay for it, you are left with half of what you thought you had. To avoid this, fill the cup, then pound on the slushie receptacle on the counter to deflate the ice faster, thereby filling your cup with more slushie goodness.
Always use a regular straw. Sure, the funky straws with the spoon at the end look cool, but unless you have the patience to spoon every bit of ice into your mouth, you find their true state of uselessness at the bottom of the cup when you get to the puddle of melted flavor and find your straw is not set for sucking liquids.
Never. Ever. scrape the side of your straw against slushie lid...even accidentally. This is just wrong. No one should have to endure that terrible noise. I'm pretty sure it could be considered cruel and unusual punishment.
Take a friend whenever possible.
Honor the "Any Size A Dollar" days at Maverik. They are sacred.
Now go, buy a slushie, and be happy. That's what I did.