You can be sure about the right company only after a discussion with potential partners and once you are better acquainted with their style of work. However, to begin with, you can start with a basic hygiene check, have a look at their vertical market experience, check if they have the capacity to match the scope and size of your project, evaluate their scaling capabilities, their data security measures, client testimonials and timeliness in not just delivering projects but in adopting new technologies as well.