Steps for Extracting data from CRM:

Configuration Steps:

1. Click on -> Assign Dialog RFC destination
If your default RFC destination is not a dialog RFC destination, you need to create an additional dialog RFC destination in addition and then assign it to your default RFC destination.

2. Execute Transaction SBIW in CRM

3. Open BC DataSources.

4. Click on Transfer Application Component Hierarchy
Application Component hierarchy is transferred.

5. SPRO in CRM .Go to CRM -> CRM Analytics 

6. Go to transaction SBIW -> Settings for Application specific Data Source ->Settings for BW adapter 

7. Click on Activate BW Adapter Metadata
Select the relevant data sources for CRM sales 

8. Click on Copy data sources
Say yes and proceed

9. Logon to BW system and execute transaction RSA1.
Create a source system to establish connectivity with CRM Server
A source system is created. (LSYSCRM200)(Prerequisites: Both BW and CRM should have defined Back ground, RFC users and logical systems)

10. Business content activation for CRM sales area is done

11. Click on source system and choose replicate datasources.
 

In CRM6.0, do we need to use BWA1 tcode to map the fields between CRM and BW, the way we used to do in earlier CRM versions?

Below are the steps for CRM(6.0) extraction as per my knowledge:

1. Activate the DS in RSA5.
2. Replicate into BI.
3. Schedule Init data load.
4. Schedule Delta.
5. Use Rsa3 and RSA7 tcodes to check data in CRM system.

Notes:

If you are have SAP CRM 5.x or later, you would activate the DataSources in RSA5 and maintain in RSA6 as you do for FI DataSources in R3/ECC.

The only difference in the technology is that the extraction goes through a BW Adaptor on SAP CRM and passes through a Service API to SAP BW. In the end, though, it's really no difference than FI.
 

Same as FI extractors in R3/ECC. 

After you have activated the DataSource in RSA5:

1) Go to RSA6 and click on the Enhance Extraction Structure button.
2) Append your custom fields to the structure and activate.
3) Create the User Exit in CMOD to populate the custom fields.
4) Re-activate the DataSource.
5) Test extraction in RSA3.
6) Replicate the DataSource in BW.
 

There is no interval settings required, like there are for FI. Here's the technical description of the CRM extraction process for both Full and Delta extraction.

1) SAP BW calls the BW Adapter using the Service API.
2) BW Adapter reads the data from the source table for the DataSource.
3) Selected data is converted into the extract structure as a BDoc.
4) The BDoc type determine the BAdI that is called by the BW Adapter.
5) Data Package is transferred to SAP BW using the Service API.

Some considerations for Delta are:

1) Net changes in CRM are communicated via BDoc.
2) The flow controller for BDocs calls the BW Adapter. 
3) BW Adapter checks if net change is in BDoc that's BW relevant. 
4) Non-relevant net changes are not sent to SAP BW.
5) Relevant net changes are transferred to SAP BW.
6) CRM standard DataSources use AIMD delta method.
 

CRM systems use what is called as a BW adapter to extract data - for other systems it is the Service API - hence these tcodes will be used - this is because CRM systems are based on BDocs and traditional R/3 systems are based on iDocs and ALE technology.

Tcodes: 
BWA5 is used to activate 'delta' for CRM datasource.
BWA1 is used for mapping fields in extract structure with BDoc.

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