Basically, I use the Preorder/Backorder mod to reserve items and I don't collect payment at check out. I ask customers to choose "Preorder - Payment at a later date" at the time of check out.
When the product is close to shipping, I contact customers to submit payment. I created a duplictate item, with the product name of "PAYMENT FOR xxxx". I make it a hidden item and include the URL in the email I send the customer.
This has eliminated a lot of problems. I don't have to worry about storing credit card info, dealing with expired cards, and it has virtually eliminated chargeback issues. It has eliminated problems of customers not knowing of they have paid someone or not.
If a customer does choose the wrong payment method, I politely email them that I am not currently accepting payment for the item and their credit card charge will be canceled or Pay Pal refunded. I also let them know the item is still reserved for them.
I end up with about 10% of the preorders not submitting payment, but I can deal with that.
You can check out my site and see how I handle the preorders at
www.culttvmanshop.com
Hope that helps
Steve