Over the counter Pre natal vitamins....

Fh and I do not want to wait too long to have a baby after we get married, we are not going to go out of our way to be super careful the way we are now about birth control, so I was thinking of starting the pre natal vitamins you can buy in the drug store over the counter- are they similiar to the prescription ones, and how soon do I have to start taking them... or even better how much folic acid should be in them? Are there any other important vitamins an expectant mom to be needs before getting pregnant?