I find myself making the same alterations to a small number of systems but
some of them repeatedly as I try different distros.  I try to keep some
notes but find they are inadequate and inconsistent.  It is also painful to
always make the changes manually.  I know that in large environments there
are tools such as source management systems, network installers, etc. but
they are serious overkill to the small network or individual user such as I.

It occurs to me that this is a situation many of you have faced and perhaps
conquered.  My hope is that there are some best practices people might be
willing to discuss here and that the discussion might be useful to others
besides me.  So if you have favored techniques or tools, lets hear about
them.  For example, a tool/script/etc to scan for and document changes from
a base install, a format/method for noting changes made (and when/how?), or
a reasonable means for re-asserting those changes after a system re-install
or upgrade.  Yes, it is a lot to ask but not asking helps no one.

-- 
Be who you are and say what you feel, because those who mind don't matter
and those who matter don't mind.  - Dr. Seuss