I agree with finding an experienced friend to ride with. I was also one of there's non lesson riders until I could afford to pay for them my own. I was a good rider before, but a better rider after.
The canter is like a rocking horse motion. You will need to relax your hips and back to flow with the horses movement. KEEP YOUR HEELS DOWN. That applies to every time you are on a horse, your heels must be down and your toe forward, not out to the side.
To ask the horse to slow down sit deeply in the saddle and pull back on the reins with gentle pressure. Increases the pressure if the horses isn't responding.
Watch all the instructional videos you can. YouTube can help you out a lot. I strongly suggest you learn the emergency stop. YouTube will also help.
This is A good video for the emergency stop. YouTube - Broadcast Yourself.
The best thing for you to do would be to get lessons, but if you're not able to or do not want them, please keep coming back here with questions. I'd rather you be getting some sort of help rather than none at all.