the white bumps show that the plant is getting ready to root.. once you see em you know you're getting close.
the only real key? keep the water temps between 70-78F, or 21-25C. you can risk going warmer to speed things up, but you also don't want to encourage algae on new clones or you may have to keep fighting it.
you'll see very slow results if the water is consistently below 70, and in most cases get no roots. the clone will simply stay in stasis, essentially.
__________________
i have a motto, sort of.
i jotted it down in a schoolbook diary: i aspire.
i don't know why i chose those particular words;
they're odd, and i like the ambiguity..
do i aspire to heaven or hell?
-truman capote