Some ideas that worked with my boys:
STORES are our worst nightmare!!! they don't make it easy for parents w/the candy and all the distractions.
I learned very early in the game to bring a snack/or lunch. I will usually go to the stores right before a meal. I will put my child in the shopping cart and layout his drink/snack/or sandwich and he will sit still because he was eating. I used to love to bring grapes, b/c they take a while to pull it off the branch and shoved them in their mouth, also enjoyed taking raisins, cookies etc.
VERY, VERY, IMPORTANT boys are like men!!! shopping is boring and they don't want any part of it. They need entertainment. I always made them bring their doodle board w/them. After they were done with the snack, they will doodle for me. I will say can you draw a happy face for mom? how about a sad face? how about the sun? etc. Interacting with them is important.
ANOTHER thing I will do is tell them that they can choose 3 toys to play with from the toy department to explore while mom shop. Then they had to tell me what they liked and didn't like about the toy. I made it clear before we selected the toy that we were going to explore them and play with them not buy and had them repeat to me that we were not buying it, and that I didn't want any trouble when we had to put the toys back. Either they explored or be bored while mommy shoped? which one is it.
Last resort: Get a mini DVD player and have them watch a movie while you shop. I don't recommend this because it kills a child's creativity, but sometimes you have to do whatever it takes.
Good luck!! remember to always bring a snack to the stores especially when you are at the paying lane when they are overwhelmed with all the candy around them.
let me know if any of it works for you!!
Ohhhh one more ... very important.
Before you get out of the car to your destination ask your child if he knows how to behave in such place and to tell you.
Then you tell him whatever he forgot to tell you.
Example: Right before I enter the library I tell my kids, k, before we go in, who can tell me the library rules? Be quite, do not disturb, get your books, etc. It is a prep talk. If a child breaks the rules, we go straight to the car and sit there, they hate it b/c it is boring. They say mom why are you not driving? b/c I needed to do such and such, but because of your poor behavior/rule breaking we now have to sit in the car and do nothing, and until you promise me that you will follow the rules we will just sit here and do nothing. (You will only have to do this about 3 - 4 times) untill they know you mean business. If you have to go a step futher to correct his behavior you can say he will be punished for misbehaving in public, that when you take him to a fun place he will have to wait in the car 10 minutes before he can go play.
Example: My child was difficult one time, so I grap some friends and told them that we were going to the park to have a play date. Well we got to the park, all the kids got out of the car and ran to the playground and I said to my son to wait a second. When all his friends were out and running about. I told him privately, now you will sit and watch them have fun without you for 10 minutes. Also asked him if he knows why he was being punished. He did remember sometimes they don't and we need to remind them. Then he was able to join his friends.
It could be anyplace CHUCK and CHEESE, make them wiggle in their car seat for 10 minutes that they want to get out.
It takes time to do this .... but it is worth it, b/c you don't loose time correct them in public. Use the time before you start the event.