Here are some suggestions from leaders who have learned ways to have a great cookie booth. I hope these will help you all have successful booths of your own. Good luck! [Thanks to Critter in CA for many of these suggestions!]

1. Have the Girls Sell.
   Insist that the girls sell their cookies. At 9 and 10 years old, they should be able to count back change and hand out the cookies. The adults are there in case some adult starts to bother the girls. The girls are there to sell the cookies. Remember, this is part of the learning experience!
   
   
2. Limit Your Girls.
   Have only 2 girls at any door, unless you are at an extremely busy spot. More than that and they start paying more attention to chatting than selling.
   
   
3. Use All Doors.
   If the store has more than one door, set up girls and tables at both doors. If half of the traffic goes in each door, you would lose half of your sales if you are only set up at one of the doors!
   
   
4. Involve Shy Girls.
   Give the shy girls a job and a prop. If they can't ask, they can smile and hold up a box of cookies to lure in a customer.
   
   
5. Ask On the Way Out.
   If you are in front of a store, always smile and say hello on the way in and ask them if they would like to buy on the way out. Politeness is extremely important! Hounding is very bad--it may prevent you from being allowed to come back next year. If they say they have already bought cookies, remember to say, "Thanks for supporting Girl Scouting!" because that sale did help you! If they say, "No," reply, "Have a nice day!" anyway. You're teaching good salesmanship this way and you are creating good PR for Girl Scouting. Both are very important!
   
   
6. Always Ask!
   Always ask--you will be amazed at how many people walk by thinking, "I'll buy if they ask!"
   
   
7. Focus on Selling!
   Smile, be cheerful, be attentive, be involved with selling cookies. The more effort you put into the sale the better the results will be. Some years it seems the cookies sell themselves and others are tough, but Girl Scouts and their cookies usually bring out the best in people.
   
   
8. Dress Professionally.
   Insist that your girls wear something that identifies them as Girl Scouts, preferably their vest or sash, since most people recognize them from a distance that way. How about a GS T-shirt if they don't have a vest? At the very least, their pins should be visible. All girls and adults should be dressed neatly and professionally.
   
   
9. Eating.
   Girls should not be eating at the booth sales. You can't ask for a sale if your mouth is full of food. Gross. If your booth is scheduled during a meal or snack time, have your extra adults take the girls in shifts away from the booth to have their meal.
   
   
10. Don't Get in the Way.
    Be careful that you and your table doesn't block traffic going into or out of the store. Also, be careful to stay out of the way of the Cart Catchers. If girls are allowed to stand at the exit, make sure they stand off to the side, not directly in front of the door. Not only is this safer (less likely to be accidentally decked by a shopping cart), but customers complain to the manager if we stand in their way, and we don't want that.
    
    
11. Visual Aids.
    One thing we found works the best if we have a poster telling of what they are supporting. Show the troop doing stuff: camping, helping plant flowers at the school, babysitting for the neighborhood mtg, etc. Help people to become vested in your troop--to want to be part of what you are doing. It also brings them in because they are curious, and they leave not only buying a box of cookies but they also leave thinking wow, Girl Scouts is great! And they will look for you next year!
    
    
12. Displays.
    Decorate your table with tablecloth, posters, and an attractive and interesting display. Three-dimensional displays attract attention and can be informative, too. You can even recycle your used Cookie Boxes to create tabletop displays and posters. Also, keep your table neat and tidy; drinks, purses, and other objects should be left in the car or tucked out of sight.
    
    
13. Weather and Guilt.
    Do not cancel because of weather--our best booth sale ever in Illinois was during a sleet/freezing rain storm! Everyone that wandered by to get a video, or run into the grocery store took pity on us and bought cookies. We froze our bottoms and toes off, but it was a grand sale. Use the bad weather. We always bring markers and poster board to make signs as we go and when it started to sleet we made up signs so that people would see us better. The girls used them, waving them around. By moving they stayed warmer and the people noticed the bright moving signs in the snow/ice. Use the adversity to your advantage.
    
    
14. Thank Your Merchants.
    Seriously appreciate the fact that the managers and merchants that allow you to sell are cutting into their own business to allow you to be there. They sell fewer cookies, and people have less ready cash after you get through with them. So say, "Thank you!", drop off a box of cookies with them, let them know when you arrive and when you leave. Make sure the area is cleaner than when you got there. Take all empty boxes home with you, or take them to the back of the store to their cardboard dumpster. Don't abuse the site. Make sure when you attach tape that it won't take paint off with it. Remember, without these generous people your sale would not be happening! Make it easy for them to say, "Sure, you can come back next year!"
    
    
15. Follow Up with a Thank You Note.
    At your next meeting, have the girls create a nice Thank You note to send to the store manager and anyone else who helped you with your sale. Tell them, in writing, how much you appreciate them letting you hold your sale at their location. These notes mean a lot to the store managers, and they will help you build a good relationship, so you can return next year!
    

[Source: Items 1-2, 4-9, 11, 13-14 from Critter]