Paddle length is also very important. You can not gauge the proper length of your paddle by walking into the store and finding what is comfortable. You will be paddling your canoe sitting, not standing. The best way to gauge how long of a paddle you should get is to get into your canoe, and measure the distance from the nose to the waterline. This is how long your shaft should be.
Paddles come in a wide variety of materials, sizes, styles, and prices.
You should avoid cheap, department store paddles. These will only wear your hands and arms out, and typically do not have a wide enough paddle to get the most efficiency from your stroke. The paddle you select should have a wide paddle, smooth handle, free of burrs or rough edges. It should be laminated if it is wood and the tip should be reinforced with a composite material. It should feel light and comfortable in your hand, and the grip should fit your palm well.