No, sometimes the animal won't even show signs until they are highly infested. If they start passing proglottids(the little rice looking sections that contain eggs), then you know they have tapeworms. If they don't, then you may need to do multiple fecals(the direct smear works best for this, at least for me, as well as the centrifuge because it takes all of the eggs down to the bottom of the vial, so you can get an accurate sample of the parasite load).
I have a really good book somewhere that shows life cycles and whatnot for every parasite, mammals, reptiles, avians, even sea mammals/fish. It's kind of neon green and is a paper-back with a plastic ringed binding. I'll see if I can't find it and get you the name of it. It's an easy book to learn out of.