It’s always better and helpful to debug through the code when developing an application.
In MS Dynamics CRM when we create a plugin at some point we need to debug and at the start we might get following issue (In this scenario I am using Visual Studio 2012, Visual Studio 2012 Remote Debugger and CRM 2013 on premises)
the breakpoint will not currently be hit. no symbols have been loaded
To fix this issue first you need to drop pdb file to C:\Program Files\Microsoft Dynamics CRM\Server\bin\assembly
then next thing you need to do is change Isolation Mode of plugin to None (if it is set to Sandbox) (in VS go to Crm Tools>Plugin Assemblies> Select plugin>Edit Assembly and amend it)
Once saved, deploy the plugin and all should work fine