Before you customize your ERP, make sure you have a plan in place
Microsoft Dynamics SL and GP are both great software packages with a lot of functionality right out of the box. In a perfect world, you would not need to do anything beyond install and keep it up to date, and all your business needs would be met. But of course, there will always be situations in which some customization will be required. It can be as simple as a check box is needed on a particular screen, or as complex as adding greater order entry capabilities or a 3rd party integration. It is important to remember, though, that no matter what you are doing, all customization presents some risk. Without proper documentation of your customizations, you may lose some functionality you count on when you upgrade to a new version. In a worst case scenario, you may not even be able to upgrade. For this reason, be certain that you have a well-documented plan in place before any customization is done.
It is important you and your consultant communicate clearly and effectively, and that you are provided a full and detailed set of documents showing what was customized and how. And of course, when possible all work should be done using tools designed for Microsoft Dynamics, to ensure a smooth upgrade path later on.