Candy Cries! Tantrums in Stores.

"I want that, Mommy!"  The little girl drops on the floor and screams.  "No, Daddy!  I want the candy!"  A young boy smacks his father on the leg while stopping to pay for gas.  What is a parent to do? 
If the child is still an infant, the process of learning to wait can be implemented easier than if the child is 2.5 or 3 yrs. old.  And, it's not just about learning to wait (which is called "delayed gratification"), it's also about respect, listening, understanding, and an internal sense of security.  It sounds like a lot, but we can do all that, as parents, through a few easy steps. 
1.  If you have to hurry to the store and back, leave the toddler at home because he will need to explore and interact with the environment.
2.  Prepare the child ahead of time.  "We're going to the store to buy milk.  We don't need anything else, but you can look at the toys if you can put them back when it's time to go."  Always wait for a response from the child and repeat the directions until the child responds "in kind" to the rules that you've set.
3.  Make sure to make time to take your toddler to the store, let her explore, play gently and carefully with the items in the store, and then return them to their places on the shelves.  Ex:  "Mommy, I want that teddy bear!"  "Okay, honey, I'll get it down for you, you can play with it for a minute, and then we have to put it away, okay?"  The child doesn't answer.  "Okay?"  The mother insists upon a response that shows understanding.  "Okay."  The little girl knows that she's expected to return the item.  "Look, Mommy, it has brown eyes."  "I see that."  The mom interacts with her daughter for a minute or two, then reminds her that they have to put it away.  "Do you want me to lift you up so you can put it away by yourself?"  "Yes, Mommy."  Take the time to play.  Let them explore and they'll let you set the guidelines, time lines and rules for that exploration.
4.  Avoid rewarding the child for "good" behavior by buying a toy at the end.  It's more effective to buy toys "at random".  If the child throws a tantrum in the store, simply pick her up, carry her outside the store, let her calm down, then ask if she's ready to listen, go back into the store and give her a chance to "do it over".  Give her a chance to succeed.  If the child does exactly what you ask the first time, just let it slide.  She succeeded.  A simple acknowledgment, such as "You put all the toys away after you played with them." does not judge or "over praise" the child, but provides "specific praise".  Specific praise lets the child know that the parent notices their growth, their strengths, and their accomplishments without being judgmental.  
5.  Have fun!  Kids love to have fun and actually feel more secure when we set the limits for them to have fun within.  When he's acting within the acceptable limits - meaning nothing and nobody's getting hurt - then go ahead and laugh, be silly, enjoy the precious time with your child.  It'll build happy memories for you and your child, and you can't buy those in any store!