We were very detailed in our selection process after the pains of living in a SharePoint/Nintex environment. We created business requirements, placed them into a spreadsheet, broken down by category. We then weighted the requirements individually, and as we demoed products, we filled out a rating on the sheet. Once all demos were complete, we ran calculations (rating*weight, averaged across category) to determine to 2-3 most viable products to do an in-depth demo (based on our business requirements which we supplied to the vendors) to see how they matched up with our vision.
Again, due to the pains of our previous workflow solution, we weren't messing around this time and wanted something that would go above and beyond our expectations, and not become a sticking point for our business processes.