We can go to Workflow screen and create a Workflow (I am using example of Opportunity Sales Process and stages which come with CRM 2013 Online trial)
We will first go to Settings->Process->New
Click on save . Now we start configuring the steps. We will configure the workflow for Record fields change and Click on Select:
Select the following field(As I am sending notification when record is moved to close stage)
Note: You can also configure notification when user switches Process if you Select Process in the above selection instead of stage.
Now, we will click ok and start configuring steps:
We will click on Add Step and Pick Check condition:
Click on Condition and fill the fields like suggested in the below screenshot:
Note: Please mention stage name in CAPS , else it will not work.
Now, Please click Save and close, and select a step for when condition is true. In our case, I will send a notification email to creator of opportunity, hence will pick the step for Send Email:
You can now click on Set Properties and set properties as mentioned below:
Click on Save and Close here and on workflow and Activate workflow:
Note: In case you want to send notification synchronous, you can convert this workflow to Real time workflow.
Now lets try it, Once i move stage of Opportunity to Close, Email is created for me!
Hope it helps!