Any time the spiral rule comes up, I like to point out that it's wrong. It is instructive in a way because one learns more about C declaration syntax, but it is even more instructive to recognize why it is wrong.

The spiral rule works only if there is no pointer to pointer or array of array in the type. But take this for example:

        +----------------------------+
        | +-----------------------+  |
        | | +------------------+  |  |
        | | | +-------------+  |  |  |
        | | | | +--------+  |  |  |  |
        | | | | |  +--+  |  |  |  |  |
        | | | | |  ^  |  |  |  |  |  |
    int * * ¦ ¦ ¦ xxx[1][2][3] |  |  |
     ^  | | | | |     |  |  |  |  |  |
     |  | | | | +-----+  |  |  |  |  |
     |  | | | +----------+  |  |  |  |
     |  | | +---------------+  |  |  |
     |  | ---------------------+  |  |
     |  +-------------------------+  |
     +-------------------------------+

The type of xxx is a [1-element] array of [2-element] array of [3-element] array of pointer to pointer to ints. I drew a spiral that passes through each specifier in the correct order.

Notice that to make the spiral correct it has to skip the pointer specifiers in the first three loops. This is marked by ¦. This is not mentioned in the original spiral rules and one could be forgiven to parse the expression as xxx -> [1] -> pointer -> [2] -> etc. following a spiral that doesn't skip the pointers.

The Right-Left Rule is quoted less frequently on HN but it's a correct algorithm for deciphering C types: http://cseweb.ucsd.edu/~ricko/rt_lt.rule.html

The spiral rule can be modified to process all array specifiers before all pointer specifiers, but then you'd have to specify that the order to do so is right and then left. At that point it's just the Right-Left Rule.