As a general rule you will want to price items at about 1/4 to 1/3 of their original retail price. If your item is a name-brand or boutique-brand such as OshKosh®, Gymboree®, Hanna Andersson or other higher end, you can price closer to 1/3 original retail. Clothing from Target or Wal-Mart should be priced on the lower end. For example, if a GAP t-shirt can be purchased on sale for $11.99, you can reasonably price it around $4.00 for good condition, $5.00 for excellent condition, more if the tags are still on.
A great question to ask yourself "what would I pay for this?"
The one exception to the 1/4 - 1/3 rule will be indoor/outdoor toys like kitchens and playhouses (Little Tykes type items). These types of toys are in higher demand and you can expect to get as much as 1/3-1/2 of original retail price, especially if they have only been used indoors and are in great condition.
Finally, if you are unsure of the value of certain items and want to do some research, spend some time on the Internet and "shop" for those items. eBay is a great place to comparison shop for the price of used items.
Use the following prices for ideas on how to price your items. These are good estimates based on what similar items are selling for in our area.