I usually look at the vibrancy of the tail color and the spacing/shape/definition of the saddles. The saddle watching takes some practice to notice right off the bat, but if you see a truly blood red tail, it is probably a BCC or a BCI with some BCC bred in.

As for the saddles, the BCC saddles are spaced further apart, so they have fewer than the BCI's. Also, I think the saddles look a little more defined, not so muddy/speckly on the edges. This varies a lot on a snake by snake basis, but in general I find it to be true, though a lot of BCI's bred to be clean may confuse you. Also, the saddle shape is important. Most people usually say BCC is () and BCI is {} but I think this varies way to much to tell, and I think it is hard to tell from a pic unless the pic is specifically of the saddle shape.

Anyway, Jimi would probably be the best at explaining this, but hope this gets you started.

Oh, another factor is head shape. The BCC have a bit longer/pointier snout...but again this is hard to tell unless you have a good pic or are seeing the snake in person.

Also, BCC tend to be bigger, but again, this varies so much that it isnt a good identifier.