The most common health issues are fleas and ticks.  They should prevented with collars, sprays, pills, etc. 

If your dog gets hurt you can make a splint out of a newspaper.  The dog may have to wear a cone to stop him from licking an injury or biting out stitches.  Teeth should be checked by the owner regularly. 

Abdominal thrusts can stop choking (the mixed breed page 91). 

Special care should be taken of older dogs.  An older dog can have arthritis or hip displasia, along with many other diseases  and conditions.  They can also get cancer and many things that many species are more susceptible to as they age.  

All dogs should be taken to the veterinarian at least once a year to get vaccines and check-ups.