I have sold on ebay for almost 5 years now. Name brand stuff is key....if you have a lot of non-name brand, then sell those in lots. Be reasonable on your shipping! A lot of people including myself will walk away if the shipping seems really high with a handling fee.
Gymboree, Baby Gap, Tommy will get high bids by themselves...start bid out small allowing to cover for your listing fee if sold. You will get a lot of watchers...no one will bid till last day. Have your listings end on a weekend...this will get a lot of exposure to tempt to bid or end on an evening...
I also like the "buy it nows". If I am searching for something that I want...I will go ahead and purchase if I find it at that moment instead of waiting till the end....I also have sold this way and find it a lot easier at times.
Make sure you list your terms!!! Payment within 3 days for example. Some people will take advantage and make you wait. I put that I will relist the item after 3 attempts are made to contact them. It is hard not to sound wenchy..but you will come across people that want something for nothing...remember your time is important too.
Last but not least...use the paypal shipping site to print and ship out! This will give you delivery confirmation for about 14 cents instead of wasting your gas to go to the post office and pay for the confirmation which I believe is 45 cents...you can request free pickup. Delivery confirmation is VERY IMPORTANT...you will run across people that ask were their package is...very well knowing they received the item but want ALL their money back. This way, you have online proof that it was delivered! Any auction that is over $20, make sure you insure at the buyers expense. Add this to the shipping total...saves you the aggrevation if it does get lost even though it is the buyers responsibility.
You will get a lot of great tips from other moms that ebay I am sure! The more you can do from home the better I think! I have tried co shops and find that I have to make appts and then wait while the gal goes thru all the clothes and offers me about 50 cents an item anyway...then I go back to the store and find she listed it for $5 or more! Remember, they are a business too out to make a $ like you...and not always fair...
Good luck to you! Once you get organized and up and running, you will find it works out just fine. Having a rummage sale...NOT! people don't have time anymore! One more thing...make sure your items are stain free! Look carefully! I only list items that have been worn once at the most...some people are really picky even if you put gently used..they expect new!

Take care!