disclaimer: not for the weak of mind. whee
...also, I'm not the greatest teacher in the world, but I'll tell you straight out how to get the job done the best I know (which seems to be pretty successful).
Alright, for starters, I'll be going over all the possible components for custom sections.
If you didn't already know, the most commonly used is the ordered list(ol - list=1).
We can also use the unordered list(ul - list)
Note: News has it the maximum amount of custom sections you can have is 195.
I, personally, doubt I'd ever use that many, but in some of these rare profile contests, it's good to know?lol
now for some guides:

The tricky part about having multiple custom sections is that we can't classify each list through bbcode, but what we can do is place lists inside of lists(this can give you headaches after a while).
To simplify this, I'll post an example and describe how it works afterwards.
about-
main about me section
[list=1]first custom section
[list=1]second custom section
[list=1]third custom section
[/list][/list][/list]
theme-
#about {margin-left:??px; margin-top:??px; height:??px; width:??px; overflow:hidden; overflow-y:auto;}
#about ol {position:absolute; left:??px; top:??px; height:??px; width:??px;}
#about ol ol {left:??px; top:??px; height:??px; width:??px;}
#about ol ol ol {left:??px; top:??px; height:??px; width:??px;}
note: the last custom section, can also have overflow(scrollbars).
One of the first things you'll notice while positioning is that the additional sections can only be positioned as relative to their previous section. So, if you were to reposition a section, any sections after that would also move with it.

Today, Aug. 21st '08, a small group of PD regulars had a breakthrough in custom sections. So, for starters I'd like to credit those who made it happen.
Special thanks to: Radiocarbon, Kayley FC, darkmane, and fr34x0r.
This guide has been made very simple for easy customization, so I hope no one has to ask any questions on this one. Like previously, I'll post the code first and explain any details anyone might need.
working example
about-
main about section
[list=1][list]
[*]scrollable section 1
[*]scrollable section 2
[*]scrollable section 3
[*]scrollable section 4
[*]scrollable section 5
[*]scrollable section 6
[/list][/list]
theme-
#about {margin-left:??px; margin-top:??px; height:??px; width:??px; overflow:hidden; overflow-y:auto;}
#about ol ul li {position:absolute; top:??px; left:??px; width:??px;height:??px; overflow:auto;}
#about ol ul li+li {position:absolute; top:??px; left:??px; width:??px; height:??px; overflow:auto;}
#about ol ul li+li+li {position:absolute; top:??px; left:??px; width:??px;height:??px; overflow:auto;}
#about ol ul li+li+li+li {position:absolute; top:??px; left:??px; width:??px;height:??px; overflow:auto;}
#about ol ul li+li+li+li+li {position:absolute; top:??px; left:??px; width:??px; height:??px; overflow:auto;}
#about ol ul li+li+li+li+li+li {position:absolute; top:??px; left:??px; width:??px; height:??px; overflow:auto;}
Now for a few notes: being that the main about section consists of margins, that can also be scrollable so no worries there. Like any other custom section, each li relies on the previous attributes, so you will have to be very specific on every attribute you wish to use. What you will also notice, and I find this very nice, is you don't have to position these sections relative to the previous section.
Only problem exists in IE6, as 'li+li' is not supported. But, to be honest, I think IE6 should be shot dead, and anyone still using it by choice is on some serious crack.
All-in-all, I'm very satisfied with the outcome of this custom sections breakthrough, cause this can also work as plain multiple sections, and we don't have to worry about all the positioning complications many experience with the original manner of doing these sections.
Well, happy coding to all, and I hope you enjoyed this one as much as I did.
__________________________
Well, that is all for now. I will be getting to more as time goes by, so stay tuned, figuratively speaking.