How to call a Dialog in CRM 2011 using Javascript

Let's see how to call a Dialog using Javascript in CRM 2011.
Firstly we need to find out the ID of the Dialog. This could be attained in 2 ways.

1. Search with Dialog name in Customizations.xml

For eg: If you search with your dialog name, you could find something similar to this.

<Workflow WorkflowId="{a13ad982-d812-40a0-ab67-f314cdabbd2b}" Name="MyDialog">

</Workflow>

2. Open the Dialog and press F11 to get the URL. In the URL we could find out the ID of the Dialog.

Javascript Code snippet:

var dialogId = "a13ad982-d812-40a0-ab67-f314cdabbd2b"; // This must be your Dialog ID

var returnValue = showModalDialog("/" + Xrm.Page.context.getOrgUniqueName() + "/cs/dialog/rundialog.aspx?DialogId=%7b" + dialogId + "%7d&EntityName=account&ObjectId=" + Xrm.Page.data.entity.getId());

//Optional:To save and close entity form as soon as the dialog is closed.

Xrm.Page.data.entity.save("saveandclose");

Sample Scenario  :

To open a Dialog when the user clicks on Ribbon button of the entity form.