Re: Two things....
Those things you're talking about are silly tricks for children, that's not sales. I'm (or any good sales person) not interested in you buying an extended warranty, I'm not interested in up selling you. I'm interested in getting you what you want. Now, I'm going to double check and make sure the thing you want is going to do what you actually want it to do, and if it isn't I'll suggest something else. That's my job. But I'll sell you whatever you want.
And you'll come back to me next time you need something I sell. And the next time and the next time. A customer who buys only once is the same thing as no sale at all. You'll come back to me even when a competitor has a better price and give me the opportunity to meet that price, because you know I'm not going to bullshit you. Hell, you might still buy it if I don't come off the price. You'll send your friends and family to me by the simple act of telling them where you (whose opinion they respect) bought it.
But the thing is, you will buy and you will buy it from me. You've already proven through the act of coming into the store you will respond to marketing materials and embedded calls to action (just like you did by clicking on this story then reading the comments) and you've proven you'll respond to a 3rd party (by responding to a comment). You're a guaranteed sale.
You're also on guard for all the wrong things. I wasn't kidding when I said the self informed and irritable customers were the easiest sells. There aren't any exceptions or surprises in sales, only salespeople who misread their customers and the guy with his defenses up is the easiest to turn and the easiest to keep cause it's nearly impossible to misread them.
For the time you're in my store you are the most important thing in the world to me and I'm not about to mess it up for $20. You've done everything you were directed to do and now it's my job to finish that cycle. You'll think you've won, and outsmarted the sales guy, but my wallet is the one that just got a little bigger... Enjoy your new thing and I'll see you next time.