Two things have helped me a lot, though I still have bouncy days:
-Lots and lots and lots and lots and lots and lots of sitting the trot without stirrups. With a long, RELAXED leg -- rather than trying to hold it where you would with your stirrups. Let your thigh hang down long, and keep everything loose, especially from the knee down. At the same time, think of using your lower abs to keep the front of your pelvis lifted. Will improve your balance, your core strength, and open your hips. All of which will help your canter.
-Think of the canter like opening and closing a book. Sounds weird, but bear with me. Your upper body is one side of the open book, your hips and seat bones are the spine of the book, and the shoulders and neck of the horse out in front of you are the other side of the open book. On the lift part of the canter, the book closes a bit. On the down portion, the book opens wider. Maybe I'm nuts but that came to me one day and I rode a really awesome, deep, connected canter as I pictured that. Sometimes thinking of things in weird, abstract, metaphorical terms works wonders.