Here is a list of commonly recommended notes in CRM-MD-BP-IF:
997586 FAQ - Common questions asked about Vendor Management
765236 FAQ: Queuing in CRM and R/3
1632952 Errors in BP to BP payment card replication
1654097 Request load of BP from ERP to CRM throws CCard error R1561
777965 Flow debugging information through queues
429423 CRM Release: General Analysis of the initial load
757955 Configuration of CRMC_BUT_CALL_FU
609766 Correction of BP GUIDS in CRMM_BUT_CUSTNO, BUT000
I would like to include the link to the Middleware help area as it is very relevant in this context also.
http://help.sap.com/saphelp_crm700_ehp01/helpdata/en/c3/95fc381478ab6fe10000000a11402f/frameset.htm
Go to the section 'Controlling the Message Flow and Error Handling' for valuable information ob BDocs
The following Blog goes through the various system settings required for BP data transfer to work correctly:
The following is a very useful blog on how to debug the customer delta download from ECC to CRM:
Useful wiki regarding BDoc error R11126 that is issued during BP replication: