Dead, Dead and MORE DEAD!

So I brought in a few plants for the winter, thinking they would be better off in my care then to the harsh winters....... well currently of the four plants I've brought in, all four are dead. I then purchased one more plant and that croaked before the first week was up. Not sure what I am doing to these poor plants, but my house is beginning to resemble something from the Adams Family!!! Seriously, how bad can one person be?????? I best not ask, I fear it could get worse!