How to deal with angry customer face to face?

Offer them some of my shine they will cool down

Listen to what they have to say without interruption. Give them the spill that you are taught to reel off if a dispute arises, if they interrupt say "let me finish." If they are constantly talking over you then stop and say nothing. If they do not get their way they will usually ask to speak to someone above you, don't feel offended by this they just want to deal with the person who holds most authority. What they do not realise is most corporations run by procedure so your boss will give them the same spill as you. Most complaints end up going back to wholesalers and manufacturers, far from the salesfloor.  Gone are the days when talking to management changed things. 

By law an actual sale takes place at the till point (unless online). This means customer have no right to claim false advertisement on items priced incorrectly if the mistake was genuine.  If a shop gives you those items at the incorrect price it is only out of good will, not out of law. You can also haggle/negotiate the price of anything at the sales point because that is where the contract takes place ie "I'll offer you this price for these goods, how about it?" Still I've done this and had a manager stand there pointing at the sticker dumbfounded, I said "Yes I can read the sticker, but I think it is overpriced so I'm wondering if you'd sell it to me for this?" Then I went on to to explain to him the contract of sale. Well this information sent his brain into meltdown as he stood scratching his head.  It was just too much for him to take in.  Haggling remains a foreign concept to the West, but I'd recommend it.

First and foremost, diffuse the situation to where you can control it without really setting this other person off.  Tell them you're there to help but first they need to calm down so you can understand the problem.  

Listen to what they're saying and then figure out the best and quickest solution to the problem without getting too involved and remember the customer is always right but not every time and that doesn't mean you have to give the store away to please them either.  

Each situation is and will be different but the basic line will always be the customer aint happy so its up to you to take care of it or get a Manager to help if you don't have the authority to deal with it yourself and if possible without making things worse , have another employee nearby as a witness just in case things really go south in a hurry