Establish a relationship with the best Vet you can find. Depending on the overall condition of your dog it may be advisable to have it checked every six months. Your Vet should be someone whom you trust and with whom you feel very comfortable.
Educate yourself about the conditions common to older pets and the therapies used for them. Be alert to symptoms so that you can bring them to your Vet's attention promptly.
Feed your older dog the best food you can afford. Consider feeding two small meals daily rather than one large one.
Senior pets have different nutritional requirements to younger, more active animals so be aware of overfeeding. Obesity causes health problems and puts unnecessary strain on painful joints and ageing organs. Treats designed for humans such as biscuits, chocolate etc will shorten your dogs life.
Consider using dietary supplements as additional support for dogs with common ageing ailments such as arthritis. There are a number of over-the-counter products which may be helpful to your dog.
Older dogs still require daily exercise for general health and mental well-being. Walks should be shorter but may well take just as long.
Take extra care with dental health and discuss teeth cleaning with your Vet at the regular check up.
Talk to your Vet about the frequency of vaccinations, particularly if your dog is unlikely to be in a kennel where annual boosters are a requirement.
Take extra care in controlling parasites such as fleas, tick and worms. Keep clean bedding and areas where your dog tends to rest.
Don't forget your senior dog just because it has slowed down and always seems to be asleep. Include it in activities every day.