From MediaSell

1. NEVER reuse a SKU. SKUs must be unique or you will run into problems.
2. NEVER change the condition of an existing listing. You should close the listing and open a new listing instead.
3. If you want to increase the quantity of an existing SKU, you will need to do an advanced import and be sure to check the “Allow quantity increase” box (with the "Test Only" box un-checked).
4. Auto re-pricing – items can be sent to marketplaces before the script has been run and the prices have been adjusted. We recommend using high base prices to avoid receiving sales at a loss.
5. Read over the reports after importing files. If you changed something and the report isn’t indicating that what you changed has been updated in your inventory, it might not have changed. Check some items on the "Inventory" page if you are unsure.
6. Always run a new script in test mode with the "verbose" box checked to ensure the results are what you are looking for.
7. If selling on Abe and/or Alibris, it’s best to check the “Enable auto-confirmation on marketplace (when order moved to 'In-Process')” box in the settings page when you are configuring these marketplaces. Please note that you will need to move the orders to “In Process” in order for FillZ to confirm the orders. You will be notified when you try to do this if there is a problem with an order
8. If an order cannot be fulfilled, or if it needs to be cancelled, you must move the order to the “Cancelled” folder in FillZ before the 5th of the next month to ensure you aren’t charged commission on the sale. You will also need to log into your account on the particular marketplace to issue a refund to the buyer/cancel the actual marketplace order. (
9. When entering an item into FillZ that doesn’t have an ISBN/ASIN/UPC, you will need to provide the publisher year in order for the item to be accepted by Amazon (as well as the expected title, author, media, and publisher fields). This can be added by an import in the FillZ experimental format under the header “pubdate”, or on the Inventory->Single Item->Switch to Non-Catalog Item page under Additional Attributes like this: PBYR|1975
10. Fees - You can add a credit card to the Settings->FillZ Billing page for automatic monthly payments. Alternatively, you can go to Settings->FillZ Billing and use the PayPal link to pay by PayPal. Please note that you must use the PayPal link in your FillZ account in order for your payment to be automatically applied to your account. Also, should there ever be a problem with a payment (such as a credit card expiring), you will be sent an e-mail from billing@fillz.com.
11. Automatic price conversions – FillZ automatically marks up prices for items going to Amazon.ca and Amazon.co.uk. If you would like this turned off you can do so by clicking the “Send market-specific prices as is - do not perform currency conversion” box at the bottom of the Settings page. Conversion rates can be found here: Amazon.ca · Amazon.co.uk
12. ISBN Consolidation – If you have multiple copies of the same ISBN/ASIN/UPC in the same condition listed under different SKUs in FillZ, it might be against marketplace policies to list them this way. FillZ offers ISBN consolidation to remedy this. For information about ISBN consolidation, please click here.
13. The weights that appear on the Postage page are for a single copy. If you have two copies of an item, you will need to manually double the weight you see on the postage page to have the appropriate shipping options. Please note that if you've doubled a weight for an item, it will stay that way if the item is ordered again, so you should always weigh your items to ensure the weights are close to what FillZ displays.
14. N/A items - This means that you need to take a close look at the order and check to see if you have any in stock as FillZ sees a problem. We will not send out deletes or quantity updates for orders that are N/A. Should you have copies in stock and want to ship them, you will need to update the quantity of the item in FillZ so we can update the other marketplaces.

[edit] TOP TEN THINGS FOR NEW SELLERS TO KNOW

1. Sellers Based Outside of US: If you are a seller residing outside of North America and listing items in a foreign currency, please read the information at the link below:
   http://wiki.fillz.com/wiki/index.php/Information_for_Sellers_Based_Outside_of_North_America
2. Settings Page: The first thing you should do is go through the Personal Settings page (Login to FillZ and click on "Settings"). Click on the "?" icons for help with this page, or click on the link below:
   http://wiki.fillz.com/wiki/index.php/Personal_Account_Settings
   If you don't understand any of the settings on this page, please do not hesitate to contact our Support Department.
3. Email notifications: If you're listing on Amazon and are being bombarded by email notifications, you can disable them by going to this link:
   https://secure.amazon.com/exec/panama/seller-admin/notifications/notifications
4. Browsers: FillZ is optimized for use with the FireFox browser. This doesn’t mean that you can’t use other browsers, it just functions best when you’re using FireFox. If you don’t have it, you can download it for free here:
   http://www.mozilla.com/en-US/firefox/
5. Orders: As soon as you activate your marketplaces in FillZ, we will populate your orders page with sales from the last 7 days. We do this to ensure that no orders are missed during the transition period from your old system to FillZ. You can safely move all of the orders you’ve already fulfilled to the “Cancelled” folder to ensure that you’re not charged a commission on these orders from us. Please note that the 'Cancelation Email" box on the Settings page must be blank when you do this, or the email you have filled into the "Cancelation Email" field will be sent to the buyers when you move the orders to "Cancelled" status.
6. Marketplaces: You will need your own seller account on any marketplace you plan on activating in FillZ. For example, if you want to activate AbeBooks, you’ll need to make sure that your Registration Application is complete and has been approved by AbeBooks.
7. Refunds: Refunds can't be processed through FillZ. If you can't fulfill an order for any reason, you'll need to login to the marketplace on which the order was placed and initiate a refund. Any order that you cancel on the marketplace should be moved to the "Cancelled" folder in FillZ so you're not charged a commission.
8. Order Confirmation: You can customize order confirmation, cancellation and deferred emails. You can also customize the packing slips you include with your shipment. For more information, click here: http://wiki.fillz.com/wiki/index.php/Customization_Tools
9. If you have your own website, FillZ may be able to integrate. Click on the link below for more information, or contact our Customer Support Department for details:
   http://wiki.fillz.com/wiki/index.php/FillZ_Custom
10. Support: FillZ currently has email and Live Chat Support for sellers enrolled in the Standard service. If you have any questions, you can click on the "Contact Us" link at the bottom of any FillZ web page for support. To use our Chat Room, please click on the link below for instructions:
    http://wiki.fillz.com/wiki/index.php/Contact_FillZ
    Premium Sellers have a designated Account Manager and are eligible for free phone support.

Alibris note: When Alibris is configured through FillZ we automatically email Alibris to request that they enable EDI for the account. This is what allows FillZ to retrieve orders. Until Alibris turns this on and we retrieve your first order, there is no way for FillZ to pick up your orders. Please keep an eye on your Alibris account and process your orders directly on the marketplace until the first order appears in FillZ.