Hi Sam,
In case you need to learn Document Splitting in New GL then please go through below links:
Document Splitting (SAP Library - General Ledger Accounting (FI-GL) (New))
Making Settings for Document Splitting - General Ledger Accounting (FI-GL) (New) - SAP Library
Overview of Document Splitting Process (SAP Library - General Ledger Accounting (FI-GL) (New))
http://help.sap.com/bp_retail603/BBLibrary/Documentation/165_BB_ConfigGuide_EN_BR.doc
http://qsands.com/pdfs/QSandS_NewGL_DocumentSplitting_GuideBook.pdf
http://qsands.com/pdfs/QSandS_NewGL_Document_Splitting.pdf
In case you have any specific question on document splitting then please let us know.
In case your question is answered then please let us know.
Regards
Pankaj Pareek