Watch out for signs of unprofessionalism, including the following red flags: asking to meet at night over drinks, dodging your questions about the company and their mission, and texting you pleasantries completely unrelated to your line of work (even before you start working).

Of course, a lot depends on the type of work you will be doing, but if you feel like your interaction is inappropriate to the setting and to what your work relationship calls for, then it probably is.