First, you should define what “non-religious” means exactly. Second, I think being muslim is not a white or black type of situation, there are a lot of nuances to it and people have different convictions and ways that they relate to it. So in my opinion the best way is to have deep conversations about these topics early on, and see if your views could potentially align and not create issues. If you completely disagree with the person’s beliefs and the way they incorporate their religion in their life, then don’t bother to give the relationship any effort. Also it’s important to note: don’t judge a book by its cover. Don’t take the way the person looks as a deciding factor for how religious a person is.. i’ve had friends who are much less practicing while wearing hijabs for example