Set Up Teams
Separate the kids into teams of four to six each. Assigning each team a color and having them retrieve items of only that color---the red team collects red items, and so on---ensures that an item can only be used by one team. In a small area with a limited list of items, this will help keep bickering to a minimum.
Define the Winning Conditions
There are two variant ways of setting the winning conditions in a scavenger hunt. In the first scenario, the team to bring back the most items on the list wins and gets some sort of small prize. If you are using the assigned colors, items brought back that are not a team's assigned color can count against that team. In the second scenario, each item on the list is assigned a point value, with rarer items being worth more points and common items worth more. After the hunt, the points are tallied and the team with the most wins.
Hand Out the Lists
Lists can contain both general and specific items. Indoors, lists can include things like towels, books, photos, three different types of toys or stuffed animals. Items can be themed to lead into the next activity. If you're hosting a slumber party for a group of girls, for instance, you might add items of makeup to be used in the next makeover activity. Even on theme lists, not every item has to be theme related. In larger locations, such as a mall, you can expand the list to include things like fliers, food court napkins and job applications for specific locations. If you expand the game to the whole neighborhood means specify that the kids are only allowed to collect items from neighbors. Also, make sure it's not too late in the day if you play outside the house.
Give Out Prizes
Prizes can be anything and don't have to be huge to satisfy. The winners could get the first makeovers or get to pick the first movie or what type of pizza to order. Small goody bags are also options and can contain things like pencils, toys, colored pens, notepads, candy, yo-yos, kazoos, lip gloss and such.