I'm not certain, but I think you have to believe in God first to receive angel experiences, and once you do, you can never forget them. Angels are kindly and helpful. They stand out, but look like humans. You can only tell they're angels because they can just vanish at will which is an extraordinary thing to behold. I haven't seen one in many many years and I do miss them. They are a comfort.
This post so reminds me of an experience I had many years ago. God wasn't an "issue" with me, but honestly couldn't seem to "wrap my head" around angels. I started meditation in my 20's and have kept it as a daily practice all these years. One day, the 90's, in deep meditation an angel appeared to me out of the blue. It was the most innocent looking thing I'd ever seen, much more than a baby even. Can't explain that right so won't try.
I'd been doing quite a bit of TV and radio interviewing during this period and one day, was on the "wait" line feed for on the air (radio). When you are on this feed, you can hear the guest in front of you - hear their whole segment, and I was fascinated, as this was an "angel expert", so they said. I ask the moderator if I could ask her a question and she cut me in, as it was a "call in" program.
Related the tale of seeing the angel to her (on the air, lol) and she said "oh, you saw the Hummingbird Angel, the wings moved very fast, like with the colors of the rainbow, right? Yes, I got a bit excited that she knew exactly what I'd seen. She said "that angel will bring other angels. The reason you saw it, is its a Cherub and you were near the throne."
Later on, at home I was looking through art books and all at once, there was Rubens Cherub paintings. OMG. Now don't get me wrong...the one dimensional Cherubs didn't or couldn't look exactly like what I'd seen, as this was from the higher dimensions and so fantastically multi-structured compared to a single medium painting rendering, but it was so close, remember thinking, "he must have seen them too, to be able to portray such a likeness in the flesh".