Re: Be nice to shop workers
Always remember that it's not the shop workers fault if the product you bought is crap - you can either a) get them on side to help or b) vent your frustrations at the crap product at them and try to intimidate. I'd suggest that starting at (b) will exclude (a) from ever being a possibility.
Of course, I also find that being decent to people also leaves me getting screwed over and scumbags with no sense of decency and incapable of feelings of guilt usually get their own way.
So it's your choice, be a decent person who gets screwed over, or be a scumbag who gets their own way - it's a matter of conscientious ie do you have one v does the person you're talking to have one. (honestly, sometimes I wish I didn't)