Some have more nutrients than others. Like more iron, or more folic acid. The ones I took have about 800mcg of folic acid in them and they seem to have done the trick. It's just one a day with food. It's a green bottle with a yellow cap, the brand is Spring Valley, you could just pick it up from Wal Mart.
They're pretty much all the same. If those make you sick you can take 2 Flintstones vitamins.