Number Range Buffering
Basic Introduction to NRIV
The document number is assigned in chronologically ascending order based on the table NRIV. For this, the table NRIV is locked until the application (LUW) is terminated by either a COMMIT WORK or ROLLBACK (OSS Note 639754). Another application cannot take a document number during this time. Read more 
Where does the system determine the Accounting Doc Type?
The Accounting document type is determined in various ways, according to type of transaction, for example the default can be configured in SAP Customizing Implementation Guide–>Financial Accounting–>Accounts Receivable and Accounts Payable–>Business Transactions–>Outgoing Invoices/Credit Memos–>Carry Out and Check Document Settings–>Define Default Values
However in the case where you have a sales billing document and you would like to default a specific accounting document type you should Read more
Function Modules for SD Reports and Smartforms
These function modules are great to get the information used to populate Smartforms and reports in SD.
Remember you can access the data with transaction SE37 and use the test/execute icon [F8].
SAP Tips – Billing document cancellations have hard coded copy routines
Very valuable tip on Billing document cancellations.
Routine LV60A006 is hardcoded by SAP for billing item cancellation.
Routine LV60A005 is hardcoded by SAP for billing header cancellation. Read more
Plants Abroad – Great OSS notes
Here are the OSS notes you need to know of when implementing Plants abroad in SAP: Read more
Tip – Pricing analysis
This is one good standard SAP tool for pricing analysis.
Transaction : PRCAT
The more you dig the more it is helpful
