I had a tutorial on drawing chains up before, but it was so old, horrible and outdated that it made my eyes bleed so I made a new one.

That's pretty much how I draw all the chains lately. It's made with Corel Painter in mind, but you can probably replicate the process using other stuff such as Photoshop.
In step 2 I mentioned checking "Preserve Transparency". Just to be clear, that setting stays on for the whole tutorial. Really helps with getting highlights and shadows placed right, particularly for smallish chains where it'd be easy to miss them otherwise.
Oh and the brush settings are as they appear in the Brush Creator.
You can see the results
here, for example.
Edit: If you're a Photoshop user, here's advice for creating the brush as kindly provided by *
cheshirepanda:
-Take a drawn chain image and 'Define Brush Preset'
-In 'Brush Tip Shape' under 'Brush Presets' Set Spacing to 201% (Or to what makes them evenly spaced)
-Under 'Shape Dynamics' under 'Angle Jitter', set drop down menu to 'Direction'
And theres the settings!
so usefull, but not only to make chains