I think that taking a good, organic, high potency vitamins and minerals is a wise way to supplement your diet. As to what brands, well, I like the following:
Standard Process Labs
Solaray
Carlson
Source Naturals
Natures Bounty
Eclectic Institute
Natural Factors
I don't like a multivitamin or mineral, I prefer taking the supplements separately, for example, a good, high potency "B" vitamin, 100 mg once a day, Vitamin "A" once a day,etc. There is just no way that one pill can contain all the correct amounts of vitamins and mineral, plus, the quality is not that good. But, if you insist on taking just a multivitamin, then I highly suggest taking one by Solaray, they are the best, I would also add a good multi-mineral supplement, again, Solaray makes the best.
Most folk think that eating a well-balanced meal and the the recommended daily servings of veggies and fruit is all a person needs, but that is far from true. Most food now-a-days is so overly processed that the nutrients are almost stripped and therefore, the nutritional value is very low. You definitely need to eat healthy, this will help the supplements to work, but don't just count on the diet to provide all the vitamins ,etc that your body needs.
If possible, I would also see a well-qualified Naturopath or an MD that specializes in "alternative"medicine, they have many many years of study in nutrition and all types of supplements including herbs, amino acids, etc. My main doctor back home in the sates was a naturopath, she helped me more than the conventional MD ever did. That is not to say,however, that the conventional MD should never be seen, there is a time and place for both,.
It is ok to take vitamins and minerals daily to prevent yourself from diseases. But you should take a limited amount of vitamins and minerals. Also, consult your doctor before taking any type of multivitamin.
Eating whole foods and obtaining your vitamins/minerals are going to be the best option. Even though pill forms of vitamins and minerals seem to be the healthy option, our bodies still have to work to break them down. In most cases, the pill forms are synthetic forms of the vitamins which in the long run are not the best option for your body.
What type f diet do you eat? Vegetarian, junk food, fried food, organic, etc;