For lamps, there are two conductors typically, the grounded one (also called the neutral) and the hot one. The grounded one typically go to the outer threads of the bulb where the non-grounded one goes to the button in the center.

A 5-15 (typical household plug) has a slightly larger blade on the grounded side (or looking at it from the pin side, one position counterclockwise (or anticlockwise as you would say) from the round ground pin. Not all two blade plugs however are so polarized.

This post was edited by ronnatalie on Sun, Oct 6, 13 at 4:23

You might want to consider buying a cheap extension cord, cutting off the female end and rewiring things all the way to the bulb holder. Then you end up with a new cord and a molded plug. At least that's what I do when rewiring lamps. Most of the replacement plugs seem to be of poor design or poor quality.

As ronnatalie said - the larger blade (and the ridbed side of the cord) goes to the threaded, side of the bulb socket. This should be the silver (not brass) colored screw.

This post was edited by dennisgli on Sun, Oct 6, 13 at 10:28