Better examples

Here is an example step by step:
1. Create a content type named Item.
2. Add a CCK field called Price (decimal - text field). The machine name of the field is field_price
3. Create a content type named Order.
4. Add a cck field called Price from Item (decimal - text field). The machine name of the field is field_price_from_item
5. Create a node for the Item. Enter the title and a price, example – 20.
6. Mark the node number. Lets say for the example this node id (nid) is 1.
7. Go to admin> content management> Field copying rules.
8. 'Add a copy Rule'
9. To type = order (note: this is the machine readable type, not the content name)
10. Source arg = 3 – I'll explain this in a few steps
11. Fields: field_price,field_price_from_item
12. 'Update copy rules'
13. In the URL write /node/add/order/1

Now the fun begins:
The module is checking if in the URL argument number 3 is a nid. If so it looks in that nid for the field_price and will copy it to the new created Order node.

Note: you can also copy the nid by specifying in the fields for example:
nid,field_nid_from_other_content

I'll update it as a README.TXT