[Astro]

It's pretty easy to SE http://www.fritolay.com/
Just say you bought a bag of chips and they were all crushed or it had a bug in it.
They'll send you a $5 coupon.

[riyo]

really? for the 5$?

first figure out what kind of SE you prefer to be, on the phone, face to face or online...
some people can be very calm on the phone but loose it face to face.
online is the simplest cuz you have time to think and reshape before you push "send"

it's mostly about what is it you want to gain, every gain has a different best way to get.

then start practice at the method you picked, if its face to face try avoid a ticket by bulshiting the officer, get a discount at shop or picking up a chick at a bar.
practice a sharp tongue for phone SE ect'...

any way it is a very handy skill in anything youll do in life.. but if you want to practice it for a free burger, you better off with CC scams.