From the GP Support Team comes Common Tips and Issues when Troubleshooting and Testing Integrations in Integration Manager
This is really nice. If you work with IM at all you should really bookmark this.
Common Tips and Issues when Troubleshooting and Testing Integrations in Integration Manager – Dynamics GP Support and Services Blog – Microsoft Dynamics GP – Microsoft Dynamics Community
Development & IntegrationMicrosoft & the GP Ecosystem
Archived post from 2013. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.