Eleanor, the only thing that has helped me, literally, and I do it, is take time (an incredibly long time) to get to know a person. By that I mean months! Outside looking in, this could be viewed as people having to "prove" that they are meaning well, but that is not really the case. I just need the time to experience those people in all different kinds of circumstances.
One of the things I "check" is whether their actions match their words. Another thing is getting beyond the stage of finding them "so very nice" and "so very much on the same page with me", "so much like me", "so caring"... I have come to notice that I judge more or less at first sight. Usually, if a person smiles and is superficially "nice" (more or less polite and a bit funny), they "pass". So, what I do is wait until that phase is over, until I am not "blinded" anymore and see the real them. People can hide their true selves only for so long. So, this is how long I wait and observe, with all my senses. As I do, again, need a lot of time to consciously sit down and feel my feelings towards a person (especially if those feelings are somewhere along the line "something's off", "there is that something I can't put my finger on"). Negative feelings towards a person become sensable by me only if there is absolute quiet. When I'm going for a walk and all the other emotional "rubbish" has been dealt with. That is, I think, because what I thought or felt never mattered. That flame was almost extinguished completely. What's left (with regard to the choice of people) is more like a whiff of a feeling or even "possible negative feeling" towards a person. A tiny flame would be saying too much as an analogy.
With my personal history, I do avoid men with certain professions. This has a reason, and even if people see it as prejudice, for me it really is a means of keeping me safe.
What I started doing was write a list of traits, a possible partner must have. The "musts" really are "musts". They are not too many and they're not over the top, but realistic and important traits to me. Could this mean I have missed someone special? Yes, but that's worth it. I have decided for myself that I do not have to give a chance to "anyone".
I also put up rules for myself, i.e. do not start a relationship (generally speaking) because I "click". I clicked with every single one of my male abusers in adulthood. So, despite my therapist saying she met her husband of 40 years and has not spent a day without him since, I won't do it. There is no exception.
That's all that comes to mind right now.
I think this is a real tough one. In comparison, it is so very easy to change behaviour!
Best wishes to you, Eleanor.