Removing from index

Hi,

I've been a bit daft and told git to track a logs folder on my live box.
So now I'm pushing and pulling log file between my live box and my dev
box.

I've tried adding logs into my exclude file and also running the git rm
command on *.log to remove them from the index but they're still being
tracked?

I'm new to git. Can anyone shed any light?

Cheers

Ryan