Terrific question. No easy answers.
I always try to get the most vitamins and minerals I can out of the food I eat, including organic fruits and vegetables. Just did a new e-book on Healing Vegetables you might want to take a gander at http://www.bellaonline.com/ebooks/ebook60
Next, I don't take a multivitamin, but I do take a multimineral because it's almost impossible to get enough calcium through eating, and taking just calcium puts you in danger of putting your other minerals out of balance. My husband and I both use GNC's. We've tried numerous other brands, but that works best for us.
Depending on my age and needs (I use muscle testing to see what I need), I take different vitamins and herbs daily. That only makes sense, because my stress and activity levels changes. Those are just two of the things that impact what your body needs. There's age, sleep or lack thereof, and more... NOW brand works for us and it's not too pricey. Find at your local health food store or look them up on the Web.
This is an important point. You have to find the brand and amount that works for you. For starters, if you don't have a copy of Prescription for Nutritional Healing, you might want to invest. Much better than a counselor. It has food sources of vitamins and minerals, treatment of specific ailments by vitamins and minerals, the Recommended Daily Allowances (which in my opinion and most other nutritionists I know aren't enough), how to get ready for surgery, manufacturer and distributor lists for vitamins and minerals, and just about everything you need. But...books go out of date quickly, so I also check www.pubmed.com
for the latest research on vitamins and minerals.
All this takes time and effort, but vitamins and minerals and herbs are my medicines. I'm 63 and I have no chronic or acute illnesses and a lot of energy,and take no drugs (prescribed or otherwise), so I figure I must be doing something right.
Hope this helps.
In health and wellness,