Spheres, boxes, and cylinders are good foundations. I highly, highly
recommend setting up horizon line and learn how to set up 1-point and 2-point perspective boxes so that you know what a good box looks like. Once you have that ingrained in your subconscious you can begin free-handing them.
There's a video course by Marshall Vandruff that was made in the 90s that is still a standard for teaching perspective today:https://drive.google.com/open?id=0B1j7GJFDJ6BXTHljUUlFOUVTelE
I paid $12 for it. I''m giving it to you, and whoever else wants it, for free. I highly recommend it. Vandruff speaks clear and concise about how to go about figuring out perspective and the learning basics of it.
Pic related is just doodles of me screwing around with shapes.