The first use case we found for Custom fields in Asana was for a Bug list that will be available to anyone working with us.
We are leaving the three custom fields that cam with the Template “Number of User reported, Priority, and Browser” and adding two of our own “Product” and “Does it Effect” which are both drop down lists.
“Product” shows a list of our websites/apps
and “Does it Effect” show a list with options
I would like a better name for “Does it Effect” but it seems clear on the form when a non-technical person is trying to add a new Bug report for us to review later. I’m hoping we can create some type of alert when a new bug is enter with any Does it Effect field is selected that is Red. Those bugs need immediate attention. I also hide all but our own two custom fields on the Task List but all show up on the Edit Task form.
I see using Custom Fields when you need to make sure your team is using the same terminology like in our case a product name.
I see using tags, much like you are using them, for one offs and more general keywords to help you narrow down a search. For now I don’t have a defined set or use for tags but I think we will as we use Asana more for daily task management.