How to migrate scripts from bash to dash?

I'd like to avoid installing bash on every new Debian 6 install. So I need to convert all my bash scripts to dash.
- How would you do that ?
- What are the differences between the 2 languages ?
- Are you aware of any caveat and pitfall ?
- Is it possible to automate that task ?

Solution

Here is a page that shows some Bashisms. You can use it as a guide for porting from Bash to Dash.

I don't know why you say you need to install Bash. It's listed as an essential package.