Here are the steps which were required to debug a workflow with VS2005:
1. Write the code
2. Build the workflow project.
3. Copy the latest feature.xml and workflow.xml files to the FEATURE directory.
4. Remove any existing copies of the workflow assembly from the GAC.
5. Add the latest version of the workflow assembly to the GAC.
6. Re-start IIS.
7. Install the feature with SharePoint using stsadm.
8. Activate the feature at a SharePoint site where you intend to perform the debugging.
9. Launch the web browser and go to the list that you want to associate the workflow with.
10. Associate the workflow with the list.
11. Attach the debugger to the correct IIS worker process. (W3WP)
12. Manually start the workflow.
13. Debug the workflow.
With VS 2008 the steps are:
1. Write the code.
2. Press F5 (This will build, deploys files, associates the workflow feature in SharePoint, attaches the debugger to the correct W3WP process, launches the browser).
3. Now Manually start the workflow.
4. And Debug the workflow.
Is It not easy!!!