The best thing I can suggest is to go to your local farm supply store instead of the vet, for anything but the most serious symptoms. They typically have the medications readily available for a reasonable price, and will often have people knowledgeable enough to point you in the right direction.
Case in point: My cat had a nasty eye infection, and I decided I didn't want to spend the time, effort or money to pack up the cat and go to the vet. So I went to the local farm supply store and said "hey, my cat has goopy eyes that aren't clearing up, and in fact seem to be getting worse. Do you have anything for that?"
They sold me a small tube of ophthalmic antibiotic ointment intended for cats/dogs, gave me brief instructions on how much to use and how to apply it without putting the cat's eye out, and about $10 later I was on my way home. It cleared up the cat's eyes in a couple days, and I had plenty left over and have used it on a couple occasions since then. In total, I probably saved at least $500 in vet bills, since I've used it to treat 2 cats on 2-3 occasions each over the past several years.
The same type of store will often have good wormers, earmite meds, etc., so as long as the animal has classic symptoms that are easily diagnosed (and again, if in doubt just describe the symptoms to someone working at the store), they ought to be able to help you.
Most of the small animal problems that only a vet can fix, can instead be fixed for about $0.06 at home. Large animals like horses, cows, etc. are different, and may warrant a call to an actual vet. Just about the only thing that's probably worth a visit to a vet for a cat/dog is to have them "fixed" (which really ought to be called "broken" in my opinion - not because it shouldn't be done, simply because it's removing functionality).