Firstly download the latest SDK for MS Dynamics CRM 2011 and extract to a local folder. If you open the SDK folder you could find a folder called Schemas. This folder contains a few XML schemas. If we include these schemas in Visual studio, we will have intellisense for the Customizations.xml file.
So let's do it.
Go to Visual studio and choose XML tab and then select Schemas as shown below.
You could see a XML Schemas window. Click on the add button.
Extension of Schema files is .xsd. Choose customizationssolution.xsd and 3 xsd files which starts with the name ribbon as shown.
Add them to the existing XML Schemas as shown. And the click OK.
Here we go...
Note: Ctrl+ Spacebar - For Intellisense
Please remember to follow the order. For instance as shown above, Inside <CustomActions> tag we have <CustomAction>. Hence Intellisense will show you<CustomAction> only if you get inside <CustomActions>.
Intellisense in Customizations.xml will save your valuable time.
Related article : How to place a custom button on the application ribbon of MS Dynamics CRM 2011