I've gotten a base Debian AMI up and running and now I need to know the best way to maintain it. I've ran the updates (aptitude update/upgrade) and installed/configured my software (Apache, Ruby, etc.) but if I reboot the instance or start a new one I'll have to do all this work over again.

How do you persist these types of things over a reboot? Do you build a new AMI every time you adjust some tiny piece of the system? Or is there some way to feed it a script on startup that configures it in "real-time"? I know I could go all the way with a Reductive Labs Puppet style setup but that's a bit too much for my needs right now (1-2 servers). Any best practices on this?

Update: I found a bit of information on using User-Data to run scripts at instance boot time.