There are 252 different ways. The general formula is that, for words of
n letters (not palindromes, as in the case of the next puzzle), when
grouped in this manner, there are always 2^(n+1) - 4 different readings.
This does not allow diagonal readings, such as you would get if you used
instead such a word as DIGGING, where it would be possible to pass from
one G to another G by a diagonal step.