Ebay is awesome and really easy! It will take some time to set up your ebay and paypal account, so try to do it without the kids around so you won't be distracted. I pull out the clothes that I plan to sell and carefully examine them for tears, missing buttons, stains, etc.... You will want to note any of those in your listing so that potential buyers are aware of any defects. Take your pictures of the items hanging if possible - they look better that way than laying on a floor or table. Describe your item as much as possible in your listing - color, size, brand, features such as smocking, trim, etc... Be VERY upfront on the condition of your item. Is it truly in excellent condition (only worn a few times) or is it in more of a "play" condition (with minimal piling, wear, etc...) Make sure to note if your items come from a smoke free home or a home with pets. Also come up with a return policy - I use - "Returns only accepted unless I have greatly misrepresented the item for sale, and return shipping to be paid by the buyer." Make sure you know exactly how much the shipping will cost before you list your item - don't guess or you may lose money, and don't over price your shipping to try to make more money - this will make buyers mad.
I really enjoy selling on ebay - I've sold my daughter's clothes over the past 1 1/2 years and made over $900! Good luck!