For heaven's sake! DON'T TRY TO CHAIN BELDUM!!! Not only are they in a sandstorm, not only do they have a catch rate of 1 but their only move is take down. And what happens when they run out of take-downs? They struggle to death! I can't think of anything worse [in pokemon] then seeing a shiny pokemon commit suicide.
If you've only just started chaining, do what I did and chain Shinx. You'll save yourself a lot of pain and misery. When I was first chaining, I went for ditto. It took me weeks to perfect my own technique, then I saw this thread and worked out I was doing it wrong anyway. (in the end I got a shiny ditto, with highest chain being 48). Some easy things to chain are:
Ponyta <---- Looks awesome BTW (blue fire FTW)
Magnemite
Starly
Mareep <---- Also looks awesome... And purple.
In, my opinion, beldum is one of the hardest pokes to chain successfully.