Our birds spend their entire life on their feet, so perches are one of the most important things in your cage.  Perches should be of a diameter that can easily be gripped by the canary's tiny feet, usually 1/2" to 5/8" is perfect.  The bird's foot should easily grip the perch, but its toes should not meet as they encircle the perch. 

Don't cover the perches with that sandpaper tubing that pet shops sell.  I can't imagine that it would be comfortable for our birds.  The claim of the makers of those tubes is that it keeps their toenails trimmed, but I suggest you trim them when they need it with a pair of fingernail clippers.

Wash and disinfect perches periodically, because the bird often wipes his face on the perch.  Food particles and other debris will cause bacteria to grow, so keep them clean.  The best way to clean wooden perches is with sandpaper, sanding the surface.  When you wash them, allow them to dry completely before placing them back in the cage.  Plastic perches should be washed with detergent and placed in a bleach water soak to disinfect.  Rinse and dry completely.

You'll notice that I've used the words "dry completely" several times in this section.  That is intentional, because your bird should not have to stand on damp perches.  Mold and mildew can be harmful to your canary, plus a wet perch is a perfect place for bacteria and germs. 

Perches should be placed at each end of the cage, which encourages the bird to fly between them.  Some cages come equipped with long perches that run the length of the cage, but these should be removed and cut down.  A perch along the length of the cage lets the bird hop back and forth instead of spreading its wings.

If you want a more natural environment in the cage, make perches from non-toxic tree branches.  The apple tree is a perfect species to use, but be sure that no pesticides were sprayed on the tree.  You'll want to wash the branch, soaking it in a bleach water solution.  Watch for evidence of insects.  Allow the branch to dry completely before placing it in the cage.  Wire it securely to the cage or suspend it from the cage ceiling.