Like any other programming language, you have to comment your ASP code. Case in point: I wrote some complex logic for a calendar I built last year. I needed to revisit the code and make some modifications, but I hadn't commented heavily. I had to waste time figuring out why I did certain things instead of just reading the comments I should have put into the routine.
One thing I always do is add a comment block for each subroutine I have in my ASP files. Here's a sample one:
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'
' Sub IncludeFile
'
' This routine reads a file and dumps it to the screen. It
' allows for variable names to be included instead of the
' hardcoded names required by the SSI directives.
'
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
This provides a visual break in the long code files I write and provides some useful information about the routine. You can add whatever information you need here. Some people like listing the input and output parameters, assumptions, etc.