如何编写标准Linux版本的脚本？

I'm going to rebuild my Linux box [yet] again. I have to create a few user groups, user accounts and install my standard packages. Until now I've just used the GUI tools. I was wondering if anyone has any recommendations on writing a script to create users, groups and install standard packages after I do a minimal install of my latest Fedora build? Sometimes I run Ubuntu so I'd like the script to be somewhat generic.I'm going to rebuild my Linux box [yet] again.