Well...this may turn you off or even appal you a little...
My parents were dirt poor and had 6 kids.
We spent MOST of our time outside as kids and we were also never sick.
My daughter is just turned 2 and has NEVER been sick...Ever.
Now...from my own personal experiences...
Put her outside. Preferrably underdressed. Make her stay out there until she's either shivering or cries to go inside. If you have a dog, put them outside with her. The key in keeping children healthy is building their immune system, and like any part of the human body, if you don't USE it, you lose it.
If her nose runs, let it run a little. Now, don't let it drip down her chin or anything...but my mother has a dedicated belief that a child who eats a bit of their own snot now and then will get sick less because they are ingesting and dealing with small amounts of bacteria in the snot and thus are building immuities to the bacteria without active contact with someone sick.
If she starts getting cranky like she's getting sick, feed her small amounts (totaling about 3 cups a day) of orange juice regularly (pulpy preferred as you get more active vitamin c) and give her the strongest cheese she will take. I recommend munster, it's high in bacteria but still pretty mild.
Use tomatoes! Tomatos are high in alllll sorts of beneficial acids and vitamins! It doesn't have to be spaghetti...there are tons of ways to use tomatoes!
If she gets a fever...and you can get her to sit still for a little bit, cut a small onion (doesn't matter what type really) in half and put one half in each sock (use some of dad's socks so there's room)...this will help bring down the fever without using meds. She's probably developing a tolerance for meds by this point so natural remedies will probably work best.
And my last "secret" oldie...the salt bath. Good for her, good for you, good for whatever ailement you have really...get a big box or bag of epsom salts (plain...not scented or special) and pour 1 to 2 cups in a bath. The temperature of the water depends on the ailement, as a general rule use the hottest water you can stand for skin and muscle issues, medium hot water for infections (of the skin or yeast infections), and lukewarm to cool water for fevers. Try to soak 10-20 minutes twice daily. If none of this helps, THEN go see the doctor.
Of course, limiting exposure is the first step...but alot of us simply can't do that, so make sure to always have some anti-bacterial soap handy and try to only use it in public places. Just like any other med, it will cause the viruses and bugs to grow stronger if you're constantly using it. Bacteria is good for us, and getting sick simply makes us stronger overall!