My favorite methodology is to use partner software or MSDN software (you could also use trial software) to set up an on-premise CRM server, other wise you could have pay for another CRM Online instance.
It's better for plugin development because you can attach to the sandbox worker process and debug in visual studio. You cannot do remote debugging easily when the plugins are running in CRM Online and as long as you register the assembly in sandbox
mode it is a good simulation.
Jamie Miley
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