I think you need to consider what sort of learner your child is.
I am a visual learner and I have always been an excellent speller. I learned to read early and I enjoyed it so I read a lot. Basically, after encountering words so often in my reading I was able to memorize what they "looked like". When I would try to spell a word I simply visualized the word in my mind and spelled it out loud as if I were reading it off a page. Visual learners who read regularly are generally good at spelling.
Auditory learners learn to spell differently and they may have more of a struggle because they are thinking about how a word *sounds* which, in the English language, will generally lead you astray. ;-) Such kids probably do better with phonics-style reading programs.