For those who have trouble spelling omicron: Divide it up by the two pieces in Greek ("o micron", or "small o"). (Think of the "micron" length unit or "micro" prefix.) Contrast this with omega ("o mega", "big o"). (This is also clearer with the Greek pronunciation.)

Coming from the french pronunciation, there's no confusion about that, to the point I am curious: what's the English pronunciation / where is the difficulty?