I'd recommend only using flat bricks of cream cheese, instead of spreadable or low-fat cream cheese, which is usually sold in a tub rather than in brick form.
Ensure your butter and cream cheese have fully softened before making frosting! This will result in a lump-free frosting.
Use any leftover frosting sandwiched between two graham crackers and freeze overnight like an ice cream sandwich. So good!
For a lighter, less sweet frosting, I recommend my whipped cream frosting! It's just as easy and delicious.