How do you know one of your non-physical friends (aka guides or angels) is around? There are a lot of ways. Some people feel things, some people hear them, some see things and/or the spirits themselves. I'm not much of a feeler, but I hear my guides internally, and I see internally. Lately, I'm beginning to see things externally, too.
I was teaching my Intuition Development teleclass recently, and saw a 'flashbulb' go off in the (otherwise empty) room, just a few feet away from me. It was about the size and shape of a firefly, but turned on and off much faster, at the speed of a flashbulb, which is why I'm calling it that. It could not have been a firefly, as it was broad daylight in the room, much too bright to see a firefly's light.
I have seen these before, and they are generally white or a deep, but bright, blue or purple. And I know they are caused by my guides' presence. Here's the thing -- I saw them for many years, but dismissed them as a figment of my imagination, until someone else mentioned them to me -- and showed them to me on video.
So if you have ever seen these 'flashbulbs', don't dismiss them. They are not figments of your imagination; on the contrary, I believe they are evidence of a guide's presence.