Make it into a game. Some parents expect their kid to sit there behaved when sitting there bored isn't fun. Involve them in the shopping.

My son went through a short tantrum throwing phase at around 3. If he started to throw a tantrum in a store, I would either pick him up and carry him outside and strap him in his car seat until he had calmed down (then go back in), or I would tell him "I am not going to put up with a tantrum, if you want to carry on you can do it by yourself." and just walk away, so that he thought I had gone. (Of course I could always still see him even if he thought I couldn't). It's amazing how as soon as you are out of sight they stop! At home, I would tell him, "if you want to throw a tantrum you will have to go in your room because Mummy doesn't want to see it. When you calm down we can talk about why you are so upset" I would then take him to his room and wait for him to get over it, then go in and talk to him. It didn't take too long before he realised that throwing tantrums got him absolutely nowhere. the biggest thing is to NEVER give in tpo the demands. If you do it just once you are back to square one!

Involve them in shopping, yes. Have a list, and ask him/her to help you find an item. Stuff like that will help. Do NOT offer to buy toys or whatever if they are good. They learn nothing and this will promote more tantrums if there comes a time when you can't buy them something. If a tantrum does occur: Ignore - ignore - ignore the tantrum. You cannot give into these fits or they will continue. As embarrassing as it is, just finish checking out and leave with your child in tow. Yelling, hitting, nothing will stop it. I've been there...each of my two kids had one tantrum each. That's it. They found it did no good and stopped.

tell them that if they dont be have your leaveing. if they continue the bad behavior leave. it has always worked wiht my "kids"

I feel for ya - I've been there! My daughter is the one who would do that to me. What I usually do is let her hold the grocery list and pen and as we get each item, I let her cross it off. Keeping her engaged constantly. Or, I'll keep her in conversation the whole time. Hope this helps!!

Your first strategy is to prevent the tantrum to begin with. Tell the child first, that you get to pick out what you are buying, and when they have their own money, they can pick it out. (As your child gets older, you can allow them to have a small shopping list and small amount of money, and teach them to make good shopping choices, and how to keep track of money.) Do not allow them to ask for things unless you want to present choices for them to choose from. A whole store is too much for a small child. I also let my daughter put things in the cart for me after I've picked them out, or pull things on low shelves off for me, when I tell her which thing to get. This should hopefully help them feel like they're helping you and participating. If s(he) does have a tantrum, do NOT give in. Kids tantrum for attention - in order to use that attention to force you into their way... don't let it work. When my daughter started doing that, I dropped everything, picked her up, took her OUT of the store, and put her in the car for a "time out". She NEVER once got what she wanted, and it didn't last more than a few tries before she gave up. She still sometimes asks for things, but will take an alternate suggestion instead. For example, if she asks for cookies, I'll suggest "well, we were going to pick crackers, do you want to help pick out which crackers to get?" and she'll be happy to help. Finally, I NEVER suggest making a child feel like (s)he has been left and abandoned in a public place. Your child should know you would never abandon them, no matter how badly they behave... that is emotional abuse, and about as bad as the people I have heard tell their children that they don't love them anymore when they behave badly. Just don't do it. Please!

Leave them alone when they have a bad temper.

When a child is "stuck in a rut", you need a diversion. something to completely take the child's focus off his temper tantrum. When my dog barks constantly over nothing, i distract him by feeding him dog food. it works. The same should apply to your child. When all else fails, leave the store.