First of all your dll needs to be signed.
Create a Batch file that contains these actions:
– remove previous version by using gacutil /u
– add the DLL to the GAC using gacutil.exe
– copy the pdb file to this location %systemroot%\assembly\gac_msil\
– IISRESET /NOFORCE
– open your SharePoint site
– attach your VS project to the w3wp.exe
– perform action and check if breakpoint get's hit.