The Business Rules feature is new for Dynamics CRM 2013. Each entity- including custom entities, now has a section for its Business Rules.
The easiest way to create a Business Rule is from within a form. Of course, you must have a security role which allows for customizing the entity.
Once in the form, Click on the Business Rules button at the top of your screen:
Existing Business Rules will be listed on the right side of your screen, click on New Business Rule at the bottom of your screen to create a new one:
We have an Opportunity field named Work Order Number. It is not set to visible on the Opportunity form. We want to show the Work Order Number field only if the type of Opportunity is a "Work Order".
First, give the Business Rule name. I've named this Business Rule "Show Work Order Number Field". Next, set a condition to check if the Opportunity type is "Work Order".
Then add an ACTION to perform if the CONDITION is met. In this case, we want to Set visibility:
1. Select Work Order Number from the list of Opportunity fields.
2. Click the check to save this step
3. Save the Rule
OK, Now your back in your Opportunity form. Click Body to go back to editing your form: