Beginner Gardening: ** Please Help, I am killing this plant!, 1 by dsid

dsid wrote:
I just got this plant at a yard sale 6 weeks ago. It is about 9' long and started out doing well. Slowly, the leaves are turning yellow and beginning to fall off. I had an other similar plant which I did the same exact thing to and almost killed it.

Does anyone have any idea what I am doing wrong? Also- I don't know what kind of plant it is so it's hard for me to do any research. Any assistance is appreciated-