There’s a fascinating video over on YouTube, posted by someone using the handle FortNine, which explains why failing to notice motorcycles is so common, and provides some advice on improving your awareness of motorcycles when driving.
Highly recommended.
I would only add one thing, which is not specifically about motorcycles, but is related, and important: you should always come to a complete stop at intersections. When you do that, the rest of the world (relative to you) stops moving, and makes it much easier to see objects that are in motion. Including motorcycles. And pets. And children. Get yourself into the habit. It may save a life.