The first thing to understand about Duns and Bradstreet (D&B, DnB), is that you do not HAVE to buy anything to receive a Paydex. D&B will tell you otherwise but it is not true.

The first thing to do is get a D&B number and this can be done through three ways:
First you can go online and get a number for free. It will take 30 days to get the number. It has been some people�s experience that they do not get a number after 30 days and when contacting D&B they say �all you are applying for is a marketing number and you have to buy creditbuilder.� This is not true.
Second, you can call 866-705-5711 and state you are applying for federal grants/contracts and you need a duns number. They will give it to you on the spot with no solicitations.
Finally you can purchase creditbuilder which will include a duns number and you also will get the number right away. Also if you speak to a rep on the phone they sometimes give you the option of buying creditbuilder lite. This can be different prices as it is not listed on the website but others have paid $199 or $250 for it.

This board has a howto on establishing corporate credit.