I don't like the default vim behavior of copying all text deleted with d, D, c, or C into the default register.
I've gotten around it by mapping d to "_d, c to "_c, and so on.
From my .vimrc:
"These are to cancel the default behavior of d, D, c, C
" to put the text they delete in the default register.
" Note that this means e.g. "ad won't copy the text into
" register a anymore. You have to explicitly yank it.
nnoremap d "_d
vnoremap d "_d
nnoremap D "_D
vnoremap D "_D
nnoremap c "_c
vnoremap c "_c
nnoremap C "_C
vnoremap C "_C