Most people don't have pet insurance, despite it's availability. Pets' unforeseen illnesses, accidents or conditions can be concerning, especially if an unexpected trip to the vet doesn't fit into your budget. Many dog owners skip the vet due to the cost (and it CAN be costly). Unfortunately, unless you went to veterinarian school, you might have a hard time deciphering a life threatening condition or a minor set back. Luckily vets are animal lovers by nature and I can't imagine a veterinarian refusing to treat a sick animal just because the owner doesn't have the funds. So, when you're choosing a vet, make sure he/she offers flexible, affordable payment plans.
These are things that would likely necessitate a trip to your veterinarian.
A sudden and/or uncharacteristic lack of appetite. You know your animal better than anyone and only you if your dog is acting odd. Refusal to eat could indicate an illness.
Vomiting. Most dogs vomit from time to time. But if they don't bounce back afterward, or if the vomiting continues for several hours, you want to call your vet. At the very least, you'd need to address the possible dehydration. It could also indicate a blockage somewhere in their digestive tract.
An unusually swollen ear. It's called a hematoma and it is often uncomfortable, sometimes painful for the dog. Often caused by ear mites, the dog's aggressive scratching can break open capillaries in the ear. If left untreated, it can become infected or it could rupture which would lead to surgery to repair it. For the cost of antibiotics and an office visit, it's worth being seen by a vet.
Unusual frequency in urination, uncharacteristic accidents in the home, compulsive licking to the genitals. This could indicate a bladder or urinary tract infection. Again, only a vet can diagnose that and the condition can be easily cleared with antibiotics. If left untreated, the infection can travel to kidneys and cause further damage. It's also very uncomfortable, sometimes burning or painful to the dog. Unfortunately, a lot of times the undesirable behavior will continue after the infection has cleared up. It'll be up to you to offer a refresher course in housebreaking once your dog is infection-free. If training your dog is harder the 2nd time around, I would suggest visiting www.TheHousebreaker.com for helpful suggestions.
An apparent paralysis. If your dog can no longer move a specific extremity, lower extremities or a paralysis from the neck down, there could be a pinched nerve or a ruptured disk. From personal experience, it would be helpful to know up front if your vet has the capability of making house calls if you can't physically move your pet. Only an MRI could determine nerve damage.
Lethargy. If you notice that your typically active dog is particularly "mopey" or lethargic, there's often a reason. Again, you know your pet and you know what's normal and what isn't. In the summer months, dehydration or heat stroke could be the culprit.
Establish a good rapport with your veterinarian. If you develop a relationship with your dog's physician, he or she will be more likely to be honest with you when you call with a concern. If he or she doesn't know you or your dog at all, she'll be much more likely to tell you to bring in your dog at the first sign of trouble. If she knows your animal fairly well, perhaps she'll be more apt to offer you a phone consultation if there's an obvious solution.
Remember--YOU are your pet's only advocate. Be their voice so that they can receive the care that they so deserve.