I haven't appeared in either examination as yet, but I've been preparing for TOEFL since sometime now......basically doing a lot of English grammer and reading as much as I can, to improve my vocabulary.
I know very little about IELTS apart from the fact that it is more along the lines of Science-Maths, I think. We are taught most of what is needed for that here in the 11th and 12th science classes.