Canna love full sun and grow best with a good supply of water thru the summer. Once again I recommend watering with a garden hose around the base of the plants, not overhead sprinkling. Mulching around the plants helps retain moisture.
The first picture (on the left below) is correct, the second picture (right) is incorrect
We grow the shorter varieties of Canna but stake the plants if needed. As flowers finish blooming, deadheading is required. Once all the buds on a stem are done flowering cut the stem either to the ground or cut off the top half of the stem and leave the rest of the stem and leaves to make a nice appearance.
Slugs (larger holes in the leaves with waxy trails) and spider mites (small webbing) can be a problem. Use treatments that you comfortable with such as Bayer Advanced from the box stores.
The word Canna comes from the Latin “cane” or “reed” and also attracts hummingbirds.