Molly,
In my experience it's all about the business process your reports support.
What use case your reports enable? ensure there is a clear path to answering the questions end users need. Then demonstrate to the process owner how much easier it is to execute the process using your reports, and finally partner with them to train end users.
The business process should have a define cadence (monthly or quarterly) and have a material impact on the organization results or management.
The first use case is the hardest, the second one a little bit easier (not much), and I hope the trend continues beyond that point