This is the costume I made for Halloween of 2011. The design is based primarily on the design of the Cybermen from the 1967 serial entitled "The Moonbase". For a variety of reasons - some practical, some personal - I did not attempt to create an exact duplicate of the costume from that show, but it's one of my favorite incarnations of the Cybermen and served as the most direct inspiration. The costume consists of five main features: the mask, the suit, the chest console, the boots, and the gloves. The mask is easily the most complicated piece, but actually took the least amount of time.
One of the nice things about choosing a Cyberman for a costume is that they appear different each time the monsters are resurrected on Doctor Who, so you have a lot of leeway in terms of design choices, and a lot of incarnations from which to draw inspiration. For me, the most important features to signify a Cyberman are the "handles" on their heads and the distinctive "teardrop" design of the eye holes (not yet present on the actual Moonbase Cyberman designs, and my primary reason for not trying to copy them exactly).
Besides the mask, the main things you'll need to make this costume are:
Silver paint (traditional and spray)
Trading Card Collector's Box
A clever brother with knowledge of electronics
A handy boyfriend with a circular saw
I will show you what I used and how I used it, but you're certainly not bound to my choices. Many of my specific selections were made based on what I had sitting around, and there are a lot of other ways this costume could have gone.