As abhilashhb stated, you cannot delete approval policies in 6.x. If you create the wrong one up you must copy it and select a different name for a new one. You can then mark the old one as inactive. There is a way to replace an approval policy when marking inactive such that you can update the old policy with the new one. I recommend including some kind of numbering in the names of your approval policies to help keep track of them.
If you want to experiment with approval policies with out leaving junk in your environment, check out one of the hands on labs for a few hours and use that to try things out.