Be savvy about your dog, and know his limits, dogs love to run alongside their owners, but not taking into account your dog's limitations is not doing right by your new running partner.
All dogs can sprint, but not many dogs are designed for long distance runs. It is a good idea to know the specifics of your dog breed, or cross breed background before you map out your course and load any time/distance expectations. Your vet can be very helpful in terms of any questions you may have, and logic dictates you can have greater expectations of an athletic Grey Hound than a Miniature Schnauzer.
Keep in mind where you are running, what time of the day you are running and how well your dog responds to instruction. Keeping to low-density traffic areas, and times of the day is probably a good idea if your dog cannot heal on command or likes to chase things.
Watch the seasons. He can easily dehydrate on a summer's day without moving an inch, let alone exerting ourselves on a mid-afternoon run. I always run my dogs early morning during summer to avoid the heat, and I always make sure they have access to fresh water at points along the run.
Very young dogs, overweight dogs or old dogs, may find it difficult to muster up the energy for even a short distance jog, so perhaps a walk is a better option.