To control flies, ticks, lice, mites in all domestic pets (except cats).
Some dogs are very destructive with their toys. Even dogs that are generally pretty good can be VERY destructive sometimes.
To put it simply, put something on you and your dog to make you both as visible as possible. The brightest colors are best and a flashing light such as a bicycle light that flashes are worth their weight in gold.
That all depends on your pet.
Factors include: his hair coat, hair length, how often he gets dirty, where he lives (if he is indoor or outdoors most of the time), shedding cycle, and any underlying skin problem.