I don't hallucinate, as a general rule, at least not very strongly.
However, when things get weird for me, I start seeing shadows and have minor hallucinations.
A few days ago, I thought I saw a spider crossing the floor. And it stopped when I looked at it. I was so convinced that there was something there, that I kneeled down on the carpet and inspected the spot. No spider.
I told my husband about this, and he said, the clue is that spiders don't stop when you look at them.
I used to hullucinate that my phone was blinking green (which would indicate a message), or that I heard my phone beep. The clue I found was that the beeping or blinking would happen after I thought about whether I had any messages on my phone.
In the movie A Beautiful Mind, the main character with schizophrenia realized that his friend wasn't real because her age never changed.
It seems that to hang onto reality, sometimes we have to see if our sensory perceptions agree with logic. If not, we might be hallucinating.
If we know it's a hallucination, then we can deal with it. It's when we're convinced that the hallucination is real, that it becomes a problem.